Tank crashing...could it be due to these?

[Aquattro]

Mason, do you run any PO4 sponge? Even though I can't measure any PO4 in my tank, I know it goes in with the food. I also know it wsn't coming out in any appreciable amount. I added phosban, and it looks like things might be coming around. I have got my temp below 80F, dosed doxycycline for 3 days, run phosban, make sure alk stays under 3.5, feed lightly, etc. So I really have no idea which one or more things is doing what. Oh, I also treated for red bugs. Next week I'll be doing a 100g water change. So much fun!!