Okay so I’m dealing with either a deficiency or a toxicity. I think. I’m growing using a marz hydro tsw 2000 in a 3x3 tent. I’m currently using dechlorinated tap water with FFOF soil. I add calmag according to directions now that I’m in week 4ish of flower and some organic bottled bloom nutes from roots organic. I noticed some mild yellowing between the veins of my leaves right after starting flower. From what I’ve read this is the early signs of CalMag deficiency. I gave the plants their normal dose of CalMag and just slightly increased the nitrogen at this point and continued to feed per directions of bloom bottles. About a week later I noticed small burn spots on the leaves that were showing the yellowing and did some reading. Based on what I found i was seeing the later signs of cal mag deficiency. Apparently the signs don’t usually show until 4 weeks after they are deficient. I increased the dosage about 50% more than instructions and came home after 5 days on holiday to this. Bare in mind I had my lights turned down from 75% to 50% to keep temps cooler since I wasn’t able to water while I was gone. Also I used strictly RO water on my last grow and was experiencing the exact same issue only it showed up later in flower and didn’t end as bad after starting the use of cal mag but it did still eventually happen. I’m very confused to be honest. I never have these problems outdoors and don’t know if it’s because of LED lights (heard they do something to cannabis plants that makes them require more cal mag or something) or if it’s my water, or maybe all of the above?! I Ph my water to 6.8 each time I water also. Oh yeah and 2 of the plants have been happy as a clam up until this point with the exact same feedings, however both of them are now starting to show a few burn spots. I’m so lost, Please help!!
Did even more reading and also thought I’d mention something else. In flower, I’ve always heard and read that your light intensity should increase gradually and the light should be closer to the canopy according to the info mars hydro provided with their light as well as many successful growers opinions on the internet. However…. I looked at the photos and read through the symptoms and progression of light burn from LED’s and am starting to wonder if that’s the problem since regardless of water source, nutes, CalMag, and other factors that could cause this issue, the light intensity and distance to canopy have both been changed at the same time (flower cycle) throughout my last two growers and the same problems occurred. I would still love to hear your opinions but thought I would add this bit of info. Thanks to ILGM for your plant diagnostics page it’s truly a wealth of information!
Thats some funky stuff thats happening to ur plant im not sure whats going with ur plant but some how i dont think cal/mag is going to fix it .it may be a potassium or phosphorus deficiency .but with ur light i wouldnt move it closer to ur plants ,i would trim those leaves cause no matter what there never going to come back ,im sure one of the other members on here will have more insight for u
This is what I’m thinking…, 
copy paste:point_down:
Black Leaves
Black leaves on plants are a big sign that something has gone wrong. While sometimes you can save these poor plants, often times things have gone too far at this stage to fix. Regardless of whether or not it is too late, figuring out what you did wrong can be a vital way to avoid these problems with your other plants.
Watering
Over-watering plants can cause a plant’s leaves to turn black. Often by this stage, the plant has irreversible rot and cannot be saved. To prevent this, don’t let your plants sit in too much water and make sure that the pot it’s in has a hole at the bottom so any excess water can escape. Before watering, test the soil by sticking a figure about an inch down. Just because the top level of soil is dry doesn’t mean the rest of the soil isn’t drenched!
It is also important to not let too much water sit on the leaves of your plants. While some can be okay, too much can lead to harmful fungal infections that can cause diseases and the eventual death of your plant. If you notice standing water on your plants, wipe it out with a cloth or paper towel to try to combat these issues
what are your runoff numbers? ph-ppm’s
looks like a little bit of heat stress
In my 4x4 I have 2 ts2000 lights and I try to maintain 18 inches to avoid light or heat stress. Like people some plants can take more some have to have less
I did test the runoff Ph suspecting it could be the problem, but it was between 6.5-7 the two times I checked it. Ppm’s I haven’t been testing because I’m not using salts and don’t typically water to the point of runoff. This is an all organic grow so never felt the need to. I will check tonight though to see.
I water my plants by the weight of the pots, so I know for certain it’s not overwatering. I’m actually thinking between light intensity, possibly warm temps (never higher than 82 but who knows), and possibly under watering that’s why they are pissed at me. It’s just weird with LED’s they run cool however I think the light intensity is sometimes way more than is needed. IMO this light is better suited for a 4x4 grow space if light intensity truly is the problem. I’m now running it at 50% power and 18” above the canopy. Time will tell!
What do you have your lights set to on the dial during flower? I moved the light to 18-20” and turned down to 50%. I was at around 12-15” and 75% so we’ll see how things progress in the next week.
Thank you for this info, I’m going to read a bit more about these deficiencies and see if maybe I need to be feeding even more 
I thought I was feeding pretty heavy but what do I know haha. Every plant is different and these may just be super hungry girls!
I had a plant that did that and I over water it to dryed out and water and cal mag it and it came back
Too many symptoms so I think it’s locking out. Since your organic I don’t know what you can do about it personally. With salt nutes you would flush and reset the feed.
one rule of thought is a good one. When in doubt flush it out. Give them a good flush and resume with feeding, also always water to run off, always. Salts can build up even if you do not think it is possible.
In addition to the changes I’ve made to the lighting intensity and light distance to canopy I plan on re-checking the ph tonight and making adjustments accordingly. Organic ph adjustments to soil are basically the same as salts except you either rely on water to slowly adjust the soil or use organic amendments added to the soil to make the change. Thanks for your help!
Live and learn Brother! We’ve all been there and you taking on an organic living soil medium was a big undertaking. I do understand the concept of keeping the medium damp and not watering to run off to keep it all balanced and your bacteria and fungi alive. A lot of soil growers experiencing PH fluctuations/ issues will top dress some Dolomite Lime, it will stabilize your PH. Not sure how that affects living soil though??
Soooo, live and learned is the statement of the day! I decided to start by testing my soil ph this morning to see if it was off. I could not believe my eyes!! My soil ph was down to 5.0!! 
I then measured my RO water ph (it was different than what I tested 3-4 weeks ago, time for new filters anyway) and it was at 7.5. This wouldn’t cause the 5.0 in my soil but took note of it anyway. I tested my dechlorinated tap water and adjusted it to 6.5-6.8 like I normally do before adding my organic nutrients. Then I began to think… I’ve been doing this step all backwards!! I mixed up a gallon of my normal bloom nutrients to the 6.8 ph water and re-tested the ph. Boy was I in for a shocker. It was 5.0! Just like the soil. I’m not normally a bottled nutrient kinda guy but in my last grow started to supplement to give an extra kick to the bloom top dressing I did. Had I known that my nutrients being added to my already ph’ed water was going to lower it even more I would have never had this problem 
Noob mistake but this whole bottled organic nutrient feeding thing is new to me. Also, I’ve still got some time in flower to get these girls back to par. after having my epiphany I slowly flushed each plant with plain water at 7.1 in hopes that it would offset the 5.0 soil. I then watered with a full nutrient solution that was ph’ed to 6.8 and vacuumed up the water from the drain pans. Lastly I removed the necrotic leaves and trimmed the dead portions off the partially dead leaves. Maybe the green portions can remain productive. I know the yellow and dead leaves won’t return to life but I want to retain as much photosynthesizing material as I can at this point. Thank you again to everyone for your help and inputs!! I will post pics in a week to see how they look.
You were right on the money with checking the ph 
Thanks for the suggestion mate!