What deficiency is this?

[desiBud420]

I'm about 3 days away from entering flowering after a 3 month veg. I flushed Plant yesterday fully.

The top half of the plant is showered with a big 85W White CFL. The top half also has this going on with my leaf edges:

This has been present for a good 2-3 weeks now, slowly increasing tipping upwards and almost proceeding towards curling in itself. I thought it was the light being too close but no. I moved light farther up by 6 inches (as it's already a 26" height, and sitting with another at 30" and movement was overdue).

Both plants have been treated the same almost in terms of soil composite, nutrient feeds (all at 1/4 to 1/2 dose, only recently a full dose as growth was stunted and nitrogen deficiency came about on one, and a slight phosphorous one on the second. Have no access to various nutrient feeds like tiger look series, or any hydroponics liquid magic but only an NPK 20-20-20 available locally. I've had no major deficiency issue in the past just a quite journey upwards except few minors. Been growing in 3 gallon pots where root tips are showing underneath, but only very so slightly.

Am I experiencing a deficiency or symptom of sorts? If so, or not, can anyone recommend something more organic as I cannot find readily manufactured products like calmag, ph up/down, or any other hydroponics liquid chemical mixtures here as mentioned earlier.
I'm in a very low-tech agricultural country and the best I could find was something with a 20-20-20 NPK, nothing specifically for veg/flower/bud stages. Just dried Cow manure and some spaghnum p.m, soilless mix, and some grow nutrients.

Please ask if you need some other information from me regarding your diagnosis. Thanks!!

Do Epsom salts have anything to do with this?

 

[Weaselcracker]

IMO it is heat stress. Leaf cupping or tacoing can occur in conjunction with nute burn as well, but most commonly is seen as a symptom of overheating. The leaf is attempting to reduce it's exposed surface area. Hot spots can occur under the lights even if overall temps aren't excessive. Movement fans blowing above the plants can help reduce this.

 

[desiBud420]

IMO it is heat stress. Leaf cupping or tacoing can occur in conjunction with nute burn as well, but most commonly is seen as a symptom of overheating. The leaf is attempting to reduce it's exposed surface area. Hot spots can occur under the lights even if overall temps aren't excessive. Movement fans blowing above the plants can help reduce this.

I'll be gentle on nutrients. In fact I may not be able to use the 20-20-20 I have in flowering cause there will be way too much N than necessary and leave it to the my soil mix to ask eke care of things. I've moved both top lights to 6 inches higher as I noticed some initial cupping on the other smaller height plant. Got a small usb fan taking care of the top area too. I'm ass using a notable change in a few days for an update.

Thanks WC!

 

[Weaselcracker]

You're welcome. You might want to consider a bigger fan- like the regular desktop style that swivels back and forth. It can work wonders for evening out temps, and also in keeping mold at bay if you have high humidity as I do. Yes the 20/20/20 would be wrong for flowering, though I don't know what to suggest as an alternate since I don't know what's available to you and aren't a soil grower. Best of luck with the grow.

 

[Weaselcracker]

Oh and I wasn't suggesting that I might be nute burn in your case. There's no sign of that. Leaf cupping is almost always from heat stress. It can happen in cases of ph problems or nute burn as well but in those cases there would be some other fairly ugly looking symptoms along with it.