Possible problems already

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Hello all , im just wondering what the problem is with a couple of these plants . There are 3 OG kush plants and 2 mendocino purple plants . A friend of mine was growing these two strains (from clone) and ended up with a few seeds from both plants (5 kush & 3 purple seeds) . So i decided to see what i could do with them . On May 30th i put the seeds inbetween damp paper towels , a couple of days later i checked on them 3 kush and 2 purple seeds had cracked open so i planted them . For this grow im using the Fox Farm Ocean Forest soil and the GB , BB , TB fertilizers . I put the new seedlings in small 4in x 4in (FFOF) pots and waterd with distilled water i didnt add any fertilizer while thay where in the small pots . Around the 16th June it was time to transplant them into larger pots the ones im using are 5in x 5in x 6in . I carried on watering with just distilled water for the first week then thought it was about time to add a little Grow Big . To be on the safe side i mixed it alot less than the 1/4 strength what people suggest on here . I`ve only waterd once with the Grow Big i switched back to plain distilled water after i started to notice that a couple of the leaves on two of the OG kush plants started to curl up . Im not sure whats causing this because the other 3 plants look ok and growth on all 5 plants seems to be good . I cant figure out if the problem is heat in the cabinet the temps in there range from 81 when the lights on to 70 when off, or something going on under the soil . I was just wondering if anybody knows what could be making the leaves do this . All help , tips and criticism is appreciated ...many thanks...

 

[Captain Kronic]

81 could be a lil much for them babies... that curl looks like a lil heat stress to me. Try getting the heat down a lil bit.
Aside from using C02, the accepted ideal temps are in the range of 72-76, of course those are optimal... you don't have to keep it exactly in that range, it's just something to shoot for!

 

[SourSkunkD]

lookin clean bro! also try spring water rather then distilled its worked for me!