I have a 2 month old 55 gallon tank. I have already made huge mistakes starting with to many fish to early. So I have fought the nitrite and nitrates from the beginning. Not wanting my fish to die I performed the 25% water changes every other day, I made it through. I currently have 2 Cichilids, 1 blue gourami, 3 bala sharks and 1 dragon fish. 1 of the balas has got a puffy eye and swimming funny so I treated the tank with malchite green. I left the lights off and covered I it for 24 hs. Then I put the carbon back in over the back filter did a 50 % water change. Treated tap water like always and now my ph is at 8.4. I have really old seashells in there that have been in tanks before and have been in this tank since start up and ph has never been this high. Could my tap water been having a bad day? Also the fish looked good yesterday but another bala has got a cloudy puffy eye and isn't a stable swimmer. Do I need to treat the tank again, How are they getting sick when they've been fine and water was good? Please help