Are you sure that's NL? That's either not NL [cos it looks sativa dominant, big time] or you've got so little light it's stretched so much it looks like a sativa.
I've grown NL many times, NEVER looked like this...
Dont tell me you got your genetics from nirvana? Ha, that'd be hillarious!
Keep and eye on your watering, that's probably whats causing the slight curling.
But who told you it was NL?
I'd get some more lights mate, keep em close and keep doing what your doing. Apart from the stretching and the fact its probably not NL its looking healthy.