Sad day for adidas fish, what happend can you help

[Tarolisol]

Well as most of you know i am/was babysitting adidas fish. Well heres the story, The fish came to me with a slight case of ick, which ran its course a couple times with no deaths or the fish stopping eating. Then after the ick was gone a couple weeks later the mayhem begins. The fish seemed to get sick. fast breathing and red gills. Then over the course of a day the fish would die. The fish looks fine exept for the red gills. The only fish that has managed to live is a hardy clown. Any ideas what it could be?