Green Crack with brown tips, curling up. Cant seem to fix. Happened twice now.

I have spent a lot of time looking around but can't tell for certain what the issue is.

Just the one plant in a tent, temps around 78 with the lights on, 72 when its dark. Running 520W cfl, the bulbs are not to close to the plant, My PH is right (6.5), I am using fox farm soil, and I have three waterings with nutes the first at 1/2 then the next two at 1/4 strength and the last water with none.

As you can see from the pics just a few certain leaves have started to curl up, they are never yellow only brown, they curl only from the tip, not from the sides. Its only happening to a few of the fan leaves. This is the second time the same thing has happened, the first time everything was the same but I was not using nutes and my solid was weeks old and I am pretty sure it was losing nutes but I dont think thats the issue as its only been in the soil for 3 weeks. I am pretty sure I am watering the correct amount each time. At this point I think I am going to up the nutes and see if that helps.

Thanks for any advice you can give to help me understand what's happening, this is my first grow and this lady is my learner so trying to soak up knowledge like she soaks up light!!!

Mg is absorbed at Ph 6.5.- 7.0 and doesn't like wet soil with high EC/ppm. U have deficiencies caused by lockout resulting in acidity. The nutes are in the soil and can't be absorbed. I'd flush the worst ones with ph 7.2 to help neutralize the soil. How about feeding half strength alternatively to plain water in abt a weeks time. Make sure pots are air light in between

lahadaextranjera said:

Mg is absorbed at Ph 6.5.- 7.0 and doesn't like wet soil with high EC/ppm. U have deficiencies caused by lockout resulting in acidity. The nutes are in the soil and can't be absorbed. I'd flush the worst ones with ph 7.2 to help neutralize the soil. How about feeding half strength alternatively to plain water in abt a weeks time. Make sure pots are air light in between

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I think it might be a K deficiency, can these two things be connected?

I'm quite sure u have a lockout. So the mutes are in the soil but can't be absorbed . I would push through water and check the ph. I'm looking at acidity. Once fixed try feed, water ,water with half strength Nutes.