how much light? got some air circulating in there? what's your room/res temps?
are you adding your nutes directly to the res? the GH 3 part advises that any fornicating between the micro and other two nute formula's (mixing them together full strength) prior to splash down will cause all sorts of problems. I'm sure you're not doing that, but just wanted to toss it out there cause I've actually seen guys in video's claiming to be top notch, pouring raw micro solution into raw grow/blossom - and the result is a batch of tobacco spit that the plants can't (according to GH) absorb.
I've had the leaves cup up like that before and it's heartbreaking to watch. Many times leaf cupping/twisting/bending/drooping occurs just prior to or immediately following lock-out. If you've noticed the plants daily growth stop dead in it's tracks(and you've seen regular sustained growth prior) you should begin gauging your PPM or EC as regularly as possible .... if the number rises substantially and/or quickly - the plants are locking out nutes. If the number falls lower, it could be a transpiration issue (got a fan blowing?)
Unfortunately, with a res that large and plants so small - it's hard to say what is going on if the PPM/EC number remains constant but the plants continue to show signs of lock-out. You want to see the plants uptaking both nutes and water equally. If one is consumed but the other ignored by the plant - you have a problem with lock out.
GH 3 part has .5 mag and 5 calcium so i doubt it's a cal/mag deficiency - but possible.
If your PH swings way up or down, that too is a tell tale sign of an imbalance in your set up (or possible borg infestation, God forbid).
r those sativa? The blades are so narrow.