Well, I don't use synthetic, chelated nutes I'm using Aurora's roots organics line, which actually suggests to mix 24 hours ahead of time to allow the pH to buffer. I was having all kinds of problems trying to adjust The pH BC I have hard water anyways, and to get it to the correct level I had to add crazy amounts of the base (just cheap aquarium buffer) way higher than the directions, and it really started fucking my plants up. In the book that came with my master pack it says to let them sit 24 hours, which ive done for a month or so with no problems, and it buffers perfectly. I have a decent air pump and I called and they told me as long as the aeration was good that I should def let it sit.
But! There was one time where I let it sit for like 3 days and it got really stagnant and rank. I noticed the smell right before watering and dumped it out and mixed new stuff and let it sit for a few hours, but it didn't buffer much. So now when I water I always smell first before feeding, but usually its fine after only 24 hours.
But, the fact that my grow is all (or mostly) organic probably makes it a lot more susceptible to mold and stuff. My ventilation is pretty good; I have an ac blowing cold air for the intake and a 435 cfm inline fan pulling through my hood and a carbon scrubber For exhaust, plus I have a 12 inch box fan and 6 inch clip fan blowing air inside of the tent, which is 4 feet by 2 feet (closer to almost 3 by almost 5). I might try unzipping the tent and setting the box fan on the floor pointing up and see if that helps. Somehow I lost my temperature/hygrometer reader and so I have no idea what my RH has been lately (it has been somewhat rainy and humid, but there was way more rain early in the grow and my humidity was fine)...
Thanks a bunch for your help guys. I'm gonna try and find some of the powder, and see what else I can do for my humidity and moisture; I saw a gnat in there the other day which I'm sure is a fungus gnat.