Any ideas how to cure it? Do I need to worry about my other fish? Its a 75 gallon tank with 3 plecos, 1 ciclid, 2 bala sharks, 2 irridecent sharks, 2 tetras, 2 silver dollars, and 2 gouramis (includes one in picture). The others seem fine. We did just have 4 barbs that all died in week from purchase.