Leaf Curl & Dimpling - any ideas?

I'm interested to see if anyone knows what causes this before I explain my setup. Any ideas?

sounds like overwatering :/

are the roots sitting in constant water? in your setup or?

Thanks, yes, I have them in Autopots but with a LED light source so very little heat, not good at this time of year for me. I have done away with the LEDs now and am moving to a traditional MH / HPS setup so all will change.
Thanks for your comments!