i wouldnt worry to much about it,,,sometimes those leaves twist up like that,,,,,is it overly hot in ya grow room?that could be the cause,what about the ph?you should put ya plant into a bigger pot now too.
i was thinking it is because i moved my 400 watt mh like 16 17 inches away from them a few days ago and it started takeing all the moisture out of the leaves before my root system could give it back so i back my light to about 22 inches going to see what it does after a couple of days yes i ph my water and it rarley gets over 85 degrees in my grow closet but it maintains a 75 80 degree temp most of the time but when the heat kicks on in my house it usully goes up to about 85 then i just open a window for a bit.
Yea mines doing same but yellowing now. I moved my lamp and put a fan in there to keep air circulating. Its not over watering tho cause then it would droop. SO make sure you have good air circulation