Curling leafs, wha is it?

all my plants are starting to curl (the leafs)

they are currently in 4" rockwool cubes in heat tray, light is on 24 hours a day


FEED:
I have had them a week (friend rooted them for me)
i have fed them baby start for the first 4 days (1/2 strength)
and for the 5th day i added vitalink growth 1/4 strength to them

i have been topping the cubes up every day

i think there isn't enough light getting to them but if there isn't does it cause this problem?

they have alot of roots

i am soon going to move to a hydroponic system


what is the problem?

sorry i have no pics
But i have a grow diary

Me being paranoid
its just a natural bend in the leaf i think

should the leafs be really dry doe?

Hmm I wish you could upload a picture. A picture is worth 1000 words.
I had a problem with the edges of the leaves curling up. It was due to my lights being too close to the plant. I backed them off and added a fan, after a few days they improved. This may or may not be your problem, sometimes different problems have similar symptoms.
Good luck