Come to think of it, I think I've been running my lights a bit too hard aswell, 4 x 480w lm301b boards with IR, far red and uv diodes in a 150cm x 300cm, I raised them a bit the other day to see if it makes any difference.
Night temps / humodity 17c / 50%
Day temps 26c / 40-45%
Nute strength...