Where is your guitars?
PLants are just fine. For an auto to grow 44" inside is fine.
Biggest issue I can tell might be inadequate lighting or my guess is that the light are too far away.
The RH is horribly high will keep buds from becoming dense. You can get nice airy buds with trichomes but, at 80% humidity during flower, you will not get dense tight nugs.
Not sure why you are flushing. Nutrient line is OK.
Making sure the lights are close enough is the first thing I would adjust, and then I would invest in a portable dehumidifier. You can drain the dehumidifier right into the tub. Make sure to get a unit that has a drain, and place it on a small pedestal the height of the edge of tub and run drain line into tub.