Leaves Yellowing from Outside Inward During Flower

[MacAndSheesh]

Long time reader, first time posting! My last few grows I have battled with yellowing leaves during flower. They seem to yellow from the outside in, eventually turning brown. I often feed at half the recommended nutes stated on the Fox Farm feeding schedule as I’ve read here it can be a bit aggressive and worry about nute burn.

That being said, I’ve been hesitant to add more than a 1tsp per gallon of calmag, but should I increase? My other thought is poor calibration/incorrect readings on my pH meter may be playing a big factor. I have an Apera pH meter arriving tomorrow as I’ve been through 2 Vivosun pH meters and was about to buy a 3rd before I finally went with Apera.

The plant I’ve included is only 1 week into 12/12, so the stretch has begun, but obviously far too early to be yellowing off.

I’m open to all constructive criticism and help you can provide!

-What strain: Snowcaine by Twenty20, photo

-Age of plant: 3 months (slow start in veg)

-Method: 80% Fox Farm Happy Frog, 20% perlite

-Nutes: Fox Farm Trio & Fox Farm CalMag

-Vessels: 5 gallon fabric pots

-PH of Water in: 6.5 - 6.7

-pH of most recent runoff: 6.1 - 6.2

-PPM of nutrient solution: 1,100 - 1,400 (feed days, depending on previous runoff), 400-500 on water w/ calmag days

-Method used to measure PH and TDS: Vivosun 3-in-1 meter (Apera kit arriving tomorrow)

-Indoor or Outdoor: 2x4 AC Infinity tent

-Light system: HLG 320W XL QB V2 R Spec

-Actual wattage: Currently at 225w at the wall, I usually increase a little more after stretch is over

-Current Light Schedule: 12/12

-Temps: 79° lights on, 68°ish lights off

-Humidity: 40% lights on, unknown lights off

-Ventilation system: 4” AC Infinity inline fan with carbon filter running to outside of tent

-AC, Humidifier, De-humidifier: None in flower except for 2 light fans pointed at canopy

-Co2: No

[VBGrower]

All I can say is, I had that VIVOSUN PH meter that came with my kit and it was trash.

I bought the same one you’re getting (PH20 or something like that), calibrated with the PH4 & PH7 solution and it has been perfect.

[Poseidon1]

Hard to say. No tds runoff numbers. No ppfd
numbers. Lockout possibly which is caused from out of whack numbers. Ph out is a bit low. Try feeding in at 6.8. Also seems to be a heavy magnesium deficiency. Again, a deficiency look can be caused by other symptoms as well. Too much light can cause a similar look as well. Notice how fresh growth looks ok? And older leafs took a beating…bottom line is multiple things can cause the same look.

[Solidgold91]

How much run off do you get vs how much you water? And welcome to the forum. Dont be bashful to post, there’s alot of help available here.

Edit: the nutrients you are using are very salt heavy and if the roots arnt flushed enough you will get lockout issues. Meaning the nutrients are there, and ppm’s look good, but the plant cant absorb what it needs.

[MacAndSheesh]

Admittedly I don’t have any readings for light intensity at the canopy, lights are about 18 inches from the canopy. Some waterings on previous grows (and this grow in late veg/early flower) I’ve had PPM in runoff spike up to 2000+, which leads me to believe a bad pH reading going in might be causing a lockout. Thats when I follow up with a flush with Sledgehammer but by that point, I struggle getting the pH of the runoff back to normal.

[MacAndSheesh]

I appreciate the welcome! I always make sure to water to (what I believe to be) a decent amount of runoff, a few cups worth, so I can try to measure pH and PPM of runoff each watering. I use a little over 1 gallon of water per 5 gallon fabric pot. Should I increase my watering?

[Storm]

That girl needs mag. Make sure ph is in line and a couple tbsp horticulture epsom salt top dressed. It has gone far but not irreversable yet. For me I would top dress it with mag. Stop feed. Phed water only. Check runoff after second or third water. If in line then restart feed. Follow nute line directions. 2nd water after restart a ph and ppm check. If in parameters soldier on. Calmag instead of just mag wont hurt at all. Add to the plain watering. Test ph of water after calmag in it and adjust if needed. There is no light stress. Most stress from lights with cannabis is heat. They are full sun plants outdoors.

[Bigb2]

I agree with @Solidgold91. If your using fox farms nutes, its helpful to follow their flush schedule.

[MacAndSheesh]

Thanks to all for the responses so far! Super cool to see some long standing forum members (whom I’ve read countless helpful responses from over the past few years!) hopping in to assist me here.

I’m going to be flushing this girl with Sledgehammer on the next watering. I try to wait for the stretch to be over to avoid stress during a crucial time, but this plant is definitely an emergency situation.

In the past, I usually rinse the flush enough to get PPM back down to a reasonable level, but my pH never seems to go back up from high 5’s to low 6’s. I’ve tried rinsing with water pH’ed to 7.0, tried top dressing soil with organic lime, etc. but pH never seems to rise back once it’s been damaged.

Any recommendations for getting soil pH (runoff, I haven’t done an actual slurry test) to rise back to an acceptable level after a flush?

[Poseidon1]

@Storm

There is no light stress.

Can you be sure of that based on the info provided? Ever hear the need of extra epsom for intense lighting? Cal mag not a magical cure all. Certainly helps. But thats a little intense for purely only epsom and or cal mag. Just saying.

[Poseidon1]

Sorry i took a while to get back to you. Ya in the 2000 tds or 4ec range, thats a little excessive for soil imo with synthetics. With your ph out being so low and runoff being so high is not generally a good thing. If you flush when the schedule calls for it, it does help. Nutrients stop being absorbed when lockout occurs and only causes the tds to rise more. Over doing cal mag will also lock out pk nutes so you know. I would not add more then whats called out.

[Storm]

@Poseidon1

not a magical cure all

I am aware of that. Just my thoughts.

[MacAndSheesh]

Quick update: On Sunday, I flushed with Sledgehammer and gallons upon gallons of water until runoff was about 650 PPM and runoff pH was about 6.5. I then did a feeding immediately following of just water and CalMag pH’ed to 6.5 (new Apera meter is great by the way!). 4 days later and it looks like things are improving! Quick comparison below (original vs today, 4 days post flush).

Moral of the story/Lesson learned: Follow the flushing schedule accordingly (every 4 weeks per Fox Farm recommendation) until I inevitably move away from to using Fox Farm nutes (I’m always open to recommendations ).

Thanks again to everyone for the help!

[Growdoc]

JACKS FOR THE WIN! Lol

[MacAndSheesh]

Back again, 9 days post flush, but now it seems to have taken a different turn?

Originally, I was experiencing extremely yellow leaves, eventually turning brown. Since then, I did a full flush (see post above) and have only watered once with just water and CalMag PH’ed to 6.5. Color eventually returned to green after about 4-5 days post flush, but now I’m seeing purple edges on some fan leaves? I’ve tried searching the forum for “dark edges”, “purple edges”, “dark tips”, etc. but nothing looks similar. It’s only about 3 weeks into flower, so I know it’s too early to start fading/showing her colors.

Any ideas? Could it be hungry and time to return to normal feeding schedule? If so, what nutrient does it appear to be lacking specifically?

[Bigb2]

What are your runoff numbers now? She’s probably is ready for nutes if you haven’t given any for 9 days after flushing. Other than the purple color the leaves look like they just have the old damage from before flush?

[MacAndSheesh]

I would say that’s a fair assessment about the lower older leaves, I did a light defol once so far, a few days after flushing, making sure to only take leaves that clearly wouldn’t recover. I certainly didn’t remove all, which were mostly lowers as you noticed.

My last PPM for runoff after flush was about 600ish (gave light feeding of calmag immediately following) and runoff pH was reading 6.5.

After my post yesterday, I fed about 3/4 the recommended dose of nutes, and this is the plant 24 hours post feed. Some more slightly purple leaves, and I can’t distinguish if the tips on the very top growth is painted nails or taking the same route…

(Up close leaf was yesterday following my update yesterday, the 2 full plant shots were taken today, post feed yesterday)