GET that light closer.... those are some spindly stretched out plants.. CLone that thing.. about 25 clones... (reduce the plants height by 1/2)

and then bring the light within 2 inches of the top.

if it were heat.. the actual leaves would be pointed up..
It is not a defciency... it is to much of something.... but I dont think its to much heat.... lol

love

bring the light closer
make sure your water is PHed to 6.8
and clone that sucker

love

plant looks good.. just watch that curling thing.. but don't stress about it.. YET.. : )