Update: It's still coming back if I don't dose and WC the tank every 3 days. It's driving me crazy. I do know that I'm having temp swings, but other than that, I've tried everything I can think of. I'm bumping up my heater to try and level everything out. I just don't know what else to do. I've cut back lighting and feeding, upped circulation, all of my parameters are normal. Anyone have any other ideas?