I have four goldfish and a pleco in a 29 gallon. I won three of the goldfish at the fair two years ago (a Sarasa Comet, a white Common and a orange Comet) and one is a store bought Shubunkin. The orange Comet has very suddenly become ill. I swear he was fine yesterday. I came home from work today and he is lethargic and rests on the bottom for a while and then he zips around the the tank and then settles down again. There is a kind of thin white film on most of his main body and he has a couple small tears in his tailfin. He also has his fins tucked most of the time. The white film is not spotted so I do not think it is ick. I tested the water and the PH is a little low but ammonia, nitrite and nitrate are perfect. I have done a large water change and cleaned the tank because the tank was due for a cleaning anyway. I have also added some aquarium salt and some Melafix. Is there anything else I can/should do? I considered quarantining him but I wonder if that might be too stressful for him at this point. Any help would be greatly appreciated.