Leaves getting curly and looking stressed

I have lowriders under 400W hps 20/4 hours light cycle.

Temperature is ok, humidity is maybe a bit low but i regularily spray water in the dark hours to make it a little higher.

They're one month and a half old, and i gave em the fertilizer two times at 50% dosage...

Everithing should be allright but leaves keep on curling like this:



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Potassium deficiency and/or heat stress. Mas potassium.

Yeah it looks like temp as Snow said and/or underwatering. Never saw a pot leaf look so much like a holly leaf.

You sure your thermometer is accurate?

Well guys i let you know the temp IS ok as the lamp is 60-70 cm (25-27 inches) distant from the plants and i'm growing in my ceiling.
At night it even gets cold up there and i have to keep an heating fan up to keep temp ok... I mounted it the way it just heats the room up without pointing directly over the plants, the way they don't feel too much and too fastly the temp shift.

I want to underline that not all the plants are having curly leaves, but just 3 out of 5 and most of all is the one in the smallest pot.

I also regularily spray some nebulized water over the leaves as soon as the light turns off...soil is always wet...

potassium deficiency? i've just looked at some photos about it but it's definitely not a potassium deficiency...

yea what that dude said

kinna lookz like a snow flake

looks like heat to me raise your light and see if the new leaves show it.

I've already done this. (this is the second topic i post as in the previous one I had been told exactly to rise the lights...but with no result)

I'm getting mad as no matter what I do but plants keep growing like that

What is your PH? Are you even measuring it? More often than not, when a plant looks retarded, its mainly related to ph problems.

I would stop spraying them and put a bowl of water on the floor to raise the humidity.

6 weeks old? It appears really small from what I can see......I've got a Lowryder 2 at 7 weeks....looks like this....
Your leaves appear to be heat stressed ....mine is under 550w hps...12/12........with lots of ventilation.