I have a double grape and a Blueberry Cheese going in promix moisture control potting mix in 3 gal fabric pots. Both are having yellowing tips starting in the margins and at the top of the plant. Watered with full strength Jack’s 3-2-1, half gallon each yesterday. Under LEDs. Anyone have any ideas?
Double Grape
Blueberry Cheese
Thanks George1961! So, I’ll just keep feeding them. Hopefully the jacks perks em back up over the next week or so. Not sure if I should feed every water or every other. Prolly give em another dose since they have only had one so far then maybe every other watering.
Personally I’d water, water then feed.
How close is the light to the canopy and also what light is being used?? Potassium and light burn look very alike.
I have a DIY Bridgelux build on a xlg-240 running about 70-80% on the dimmer. It was only about 4 inches from the canopy, its now about 8 inches. They got moved the day before yesterday.
Yeah I think the light is burning them bro. Bridgelux strips are bright AF and put out a lot of heat. I think you’ve found your issue. I know led can be kept close to the canopy but I reckon 12 inch is more than close enough. I run solstrips and have to keep them 12 inch away from my canopy.
Thanks for the advice! I’ll move the light a little bit further and see if that takes care of the issue.
Your welcome mate. The plant will bounce back but the burned leaves will likely go brown and drop of the plant but you’ll see new growth quickly though. 
If nothing previously said fits try sulfur deficiency or high TDS in water.
Blueberry Cheese seems to be bouncing back, Double Grape is getting worse. Gave em each half a gallon of pHd water last night. Double Grape has been drooping for awhile and the yellowing is getting worse. Took off a few of the bad leaves last night.
Put dry towels underneath the container. It will draw the water out. Suck it dry. They are in shock. Some guys told you some stuff.
Like fast within a few minutes. Don’t be afraid to use a big towel. Don’t leave the towel to long. It’s not a drain pan. It will mold.
Can you check ppm and pH from runoff? 
I dont really have a way to collect runoff, just a big dog pen pan to protect the wood. I haven’t watered to runoff yet either. It holds the whole half gallon I’ve been giving em.
@Hemp, what will sucking the water out do? It was dry before I watered them, so I don’t think it’s over-watering.
If you ever do that will help if you’re getting water stress.
I see, I was wondering if those nutrient deficiencies while having food available could be because of a pH unbalance, that could also provoque a lockout as suggested, what’s your watering pH?
Anyway you take it easy I wish you the best
Thanks for the tip @Hemp! I’m thinking of watering for runoff to test the pH, and I can do that after to suck some of the excess water off.
@George, I’ve been wondering about pH too. Initially just tap water at 7pH, now I’m bringing it to about 6 the last few waterings. 6.1 on the last and 6.0 the time before. I had issues with pH with my last hydro run. I think my tap water sucks. I’ll try and get some runoff to test tonight maybe.
That could be the cause, at least in the initial stage, many nutrients are out of range with pH 7.0:
But I see the new growth is also affected, so that makes me think again about that nutrient lockout. Try to flush with just pHed water (distilled ot RO would be great) and see the results … 
