Many thanks for the feedback PJ and Stinky.

I have a carbon filter hooked up to the extractor and an intake hose, good circulation going through there as if I hold a thin piece of thread next to the intake vent, it gets sucked in. Should be plenty of fresh air being taken in.

I've moved the lights up a tad as the temp monitor I had seemed to be giving funny readings. Got a new one in there and the temps around the plants were varing by about 10 degrees F with this second monitor. It's sitting at about 80 degrees F now.

Thanks for the tip on the ph tester PJ, will be look in to that ASAP. Have been looking at all kinds of devices and from reading other threads, it seems a wise decision to invest a bit of cash in to a decent ph kit.

I will get a few full pics up of the plants next time I have a chance, just sorted them out and all the new growth coming through is nice and green. Yellow/brown colouring of the bottom leaves haven't increased since my original post, so fingers crossed it was either a bit of heat stress or as you say Stinky, lack of a bit of N and the plant had been sucking it in from them.

Thanks again people, help is much appreciated. Will get pics up ASAP.

Cheers.