You only get negative pressure when it is hot? That makes absolutely no sense. Negative pressure is created when your extractor fan is pulling more air than you are supplying to the tent. Also what is an intractor? It seems like you are getting ahead of yourself on the skills you are trying to master. I would suggest reading a lot and doing things simple for now. You are complicating this too much for yourself and it seems your logic is not very correct at this point.
It is made in this way because need lot of fresh cold air to keep the tent on a normal temperature, i've tried also to keep it in negative pressure. Increase temperature, fresh air coming inside is not enough.
I deal with the smell with an ozonizer inside this room with the door closed. That also contribute to keep the room cold.
Plant after add inside more W:B spectrum.. started to recover. It was not the nutes, it was not a burn, it was not the ph, it was the Light for this stage. Since, as i said, there was no nutes extra added in THE SECOND WEEK OF THE PLANT!!!!!!
Extractor -> Takes out
Intractor -> Puts in
Same, but reverse side. Efficency is much higher when you put in instead of take out. With the light changes, all plants are developing and growing healthy. Will put some extra pictures soon their start to flowering.
This is how the tent looks now. Two lamps 300x3W/300(6x50 COB) output around 60.000LMX at 75cm.
The plants that are at the right, are the plants we were talking about. I changed the pot of some them to higher 4gal (fill with earth till almost 3-3.5gals) 20/4H. CO2+ 1100-1200ppm.
I have also installed inside a small "ozonizer/filter" that works when plants are "sleeping". CO2 is only added when light is on.
Seems that now is all under control. Since i put this big new light, plants are stunning. I guess they are happy with this new light...
Regards