The heater instructions said to unplug if it got over 82 F. I read somewhere that the 75-80 F range is a good target so that is what I am aiming for too. The problems I have seen are yellowing leaves and some leaves brown and die - that is normal. I did cuts from the MK a couple of weeks into Veg and they reverted just fine. Did I mention to keep the clones under 24/0 light? Preferably CFL or fluor tubes. If under a HID keep them several feet away they they don't get burned.