Plant Problem - lobster claw

I have a sativa plant that is 2 foot tall and about 2 or 3 months old that is lobster clawing on me. The leaves on the new growth are curling down in a lobster claw shape, no yellowing. The leaves that are curling are also turning a little dark green and drying out to a crumble. It started over night after a good water. I have in the past given them a light water, dry out, feed, dry out, heavy water, dry out, and then start over. Out of 7 plants only one is doing this. Good light, ph at 7 to 6.5, 65 to 75 degrees. I use spring fed lake water. Can you help me explain why this one plant went lobster claw on me? Thanks JOHN

Slide the plant out of its' container when it dries, it may be root bound.

Either root bound or over fertilized. Clawing and dark green is usually a sign of too much nitrogen. Good Luck

Sounds like overfert to me.

got a pic?