I am very worried abut my RTC. He is staying at the bottom of the tank but will flip himself over onto his back. He seems to be swimming sideways and has problems leveling himself. He also does not seem to want to eat. My ph level is 6.0ish and my ammonia and nitrite (nitrate) levels are fine. The tank is a 220 gallon and I have 2 other RTC and a pleco. I did a 30% water change and also cleaned the filters. There is no outward signs of illness. My buddy is about 2' long and I don't want to lose him. Does anyone have any ideas as what could be the problem?