42 Day Old Plants have rust spots and other symptoms. Advice?

This is my 3rd AF grow. 3 Bluetooth Autos and 3 Amnesia Haze Autos. LST.

  • 4x4 tent with five 300w LED’s (actual 70w draw). It’s a mixture of cheap LED fixtures. Run 24 hrs a day. About 18" above canopy.
  • Pro-Mix Ultimate Organic soil from the local Menards. I added some extra perlite.
  • 3 gal grow bags
  • Dyna-Gro nutes - Foilage Pro, Bloom and Mag Pro.
  • Great White and Pro Tekt supplements.
  • Room temp at canopy stays solid 74-78 deg. Humidity is at 51% varies only 2-3 points. Excellent air exchange with a 6" exhaust fan. LED lights are always on.
  • I have well water that is 450ppm. I have an RO system that drops it to 75ppm. However, I water with a 50/50 blend of RO and well water. My well water will scale up a coffee maker in no time - very high calcium? I screwed up with my last grow by using straight RO water. I know what I did wrong but it still scares the shit outta me to use it straight up, even with the proper supplements. So my blended water starts at 150- 225 depending how accurate I measure.
  • I have been watering each plant as needed. I use the “lift the pot method” to determine when to water. Each plant will vary some but will only get watered when the pot is light enough.
  • I do alternate waterings. PH’ed blended water with 5ml/1tsp Cal-Mag Plus and Great White. Then next watering w/nutes. When I water nutes I am using 2.5ml Dyna-Gro Bloom, 2.5ml Mag Pro, 1.25ml Pro Tekt, 1/2tsp blackstrap molasses and 5ml/1tsp Cal Mag Plus - that adds up to usually around 600-650 ppm.
  • I keep my water PH at 6.3. I always water to at least 20% runoff as that is what a gallon will do per plant normally. I religiously check my runoff PH and it is generally around 6.5.

I think that should be enough info - if I have missed something please let me know.

I have attached pictures of a few plants that seem to be having issues within the last 2-3 days. They have developed rust spots on leaves mostly near the top of the plants. But you will also see that even lower leaves have spots on them. Growth over the last 2-3 days may have slowed also. However water intake hasn’t slowed.

These pics are taken with 2 of the full spectrum 300w LED’s turned on. It’s not the burple light it’s more white/pinkish and seems to make the spots and light colors stand out more in the pic so I left them on.

PH off or fluctuations? I have monitored runoff and is around 6.5 ish.

Magnesium deficiency?

Calcium deficiency?

Deficiencies due to root lockout? But why?

I should be due to water tomorrow. Time for PHed water and Great White.



Had to edit your pictures since photo bucket spams with adds

you noted you are mixing RO and Well water with a high Calcium content before adding nutrients also that you add Cal/mag between feeds :wink:

your ppm is pretty low for flower

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Thank you for the reply! I had read that link earlier but wasn’t sure what I had here. Thank you.
My normal schedule would have me watering tmrw and the plants feel like they will need it. What would you suggest I do?
Should I flush with 3 times container size with pH’ed water and then final flush with nutes? What would you suggest my ppm be in flower, again these are autoflowers?

Some additional maybe non-related questions while I have an ear:

  1. Should I be using cal/mag every water? Or can there be too much?

  2. If I use well/RO water blended and the ppm is at say 200 and I switch to no well water just straight RO (at 75ppm) can I now add extra nutes to make up that 125ppm I just dropped by not using any well water?

Thanks again!

There most definitely can be too much most add either between feeds or at feeds not while feeding and to water cycle. You shouldn’t need to flush but simply stop adding Cal for awhile 2 feed cycles have you tested ppm of run off it would tell you if a flush would actually be in order also would give a better indicator as to feed adjustments. If your run off is 600-650 range I would revisit the feed dosing and aim for a 800-900 ppm

After reading about the relationship between phosphorus deficiency and too much LED light intensity I decided to turn off 2 of my generic 300w LED lights last night, leaving just 3 on. If I had more headroom I may have just raised the 5 lights. This morning the plants all looked much better, they had more life with leaves reaching out with absolutely no drooping. Late this afternoon I could see noticeable growth.

So… I believe I will forge ahead with a slight uptick in nutes and no cal/mag the next two feed cycles as you have suggested.

Thanks again! I will update if I have anything new and I will post a pic or too down the road.

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U should at least move them to an 18 / 6 light schedule… or maybe a 16 / 8 … they will love you for it… trust me… :wink:
Plants do all of there growing in the dark… they get all the tools ready in the day time and then they build in the dark… :wink:
:v: :sunglasses:

Plants do all of their growing in the dark?

This from Royal Queen Seeds website:
When it comes to picking the right light schedule, you need to weigh up the pros and cons to assess which is best for your situation. Personally, we have grown more under 18-hours of light, but the ones we have done under 24-hours have been very successful as well.

Some even like to take the middle ground, using a 20-hour light cycle. This offers the best of both worlds.

One thing is for sure; you do not want your autoflowering plants to receive less than 18 hours per day. This is the minimum, and anything less will adversely affect growth.

At the end of the day, each grower needs to do what works for them. It is worth experimenting with both light cycles (on two separate grows), to see what gets you better results, and what suits your grow situation better. 24-hour lighting offers greater potential, but it may not always be practical. Either way, both light cycles will see your autoflowering cannabis flourish, so happy growing!"

There’s some truth to that. But I haven’t seen any plants on 24 hours light outgrow plants on 18, not by visibly noticeable amount anyway. Maybe others have different experience though. So if both will work fine, why be more abusive to your lights and consume more energy than you need to?