prolly not nute burn. the rest of the plant looks good. Its just the plant killing off the leaves that don't get light. I don't know how they look now, but you can take out the bottom 1/3 of the those leaves and the uppers will be stronger for it. sorry haven't been on in a while.
fresh air is recommended for co2/ oxygen exchange. I'd say try a small fan in the day time to see what the temp goes to, and you can always put the heater back in the room but you shouldn't have to
take the net pots and run tap water through the whole pot making sure that goo around the roots are flushed away. The chlorine in the water will kill bacteria thats hiding and not being reached by the h202. but keep up with the h202 still
she looks good to go. I'd still rectumend tying her back a bit and giving it another week but its not my grow. think of it like this... with cfls only the top couple inches will get light so make a lot of surface area of canopy. also my fave thing to do with cfls are take the extension cords...
What is the ph of the water that goes in and the ph that runs out? I think its nute def. If the ph is off and locking out nutes, thats bad What is the NPK of what your giving. Are you using GH grow and micro?
if you raise your humidity your temp will go up higher. my 2 cents. if you're gonna raise 10% or more you need a humidifier and if you do that you might have to add more ventilation. I'd say try a pan of water and if that raises it to 40 be happy