What is the ambient air temperature and do you have exhaust and passive intake. If the tent is open air(tent open), the hot air is going to get trapped in the tent, you might as well not have them in the tent at that point. Lower temps will get the humidity better, then you might want to get a humidifier if it's still 20% which it shouldn't be. For instance, If I'm at 75-77 degrees, I'm about 49% H, if I'm at 81 with the tent open and working in there(which will go down when I close it up fast being sealed up), Humidity is about 38-40%. I live in dry Ca, and 31% h Outside today and earlier the 2x4 was 51% at 77 degrees and now it's 79 and 42%(setup runs 3 degrees above Ambient room temp like clockwork). I hit 12 zips(slightly over I'm dialing it in,i feel like there's room for improvement ) in a 2x4 with Qb's at 280 watts with 2 plants or 3 it doesn't matter(I prefer 2) so in my opinion as long as RH s not excessively bad(20% is rough for younglings), my healthy plants don't skip a beat.