In order, I would say that your exhaust is the #1 issue, followed by overwatering a soil that the lime buffer is already used up in. Wow that bad grammar was epic. In which the lime buffer has been used up? You know what I'm trying to spit out. lol

You definitely need more air flow and a good pH test and an up/down kit (The GH one comes with all 3) and get your soil pH up to 6.7 by flushing. There's a soil chem link in my sig that will help.