NFT - Plants looking ill (pics)

Hey there went into my room this afternoon to see that my girls are looking to well, last night they were looking fine.


The water PH is about 6.2~ish

I'm fairly certain I havent fertalised (if anything i under fertalised, didn't think this would be particularly bad for them though).

The lights a good 40cm above the girls, and apart from that Im really not sure whats wrong with them.


The humidity is around %70, using 2 x 600W's, good ventilation, using rockwool/clayballs, lighting cycle atm is 24hrs, 2nd week in so far

When the leaf margins roll upwards like that, it generally means the plant is trying to retain moisture. The lights may be too close, the temperature may be too high, or they may simply not be getting enough water. It's definitely indicative of an environmental problem rather than a nutrient problem.

Yea that looks a whole lot like heat stress bro. Usually what happens next is the tips will turn brown.