Whats happening to my fish?

so i did a 50% water change then the next day i saw one of my fish fin was like coming apart and then i saw other of my fish fin having the same problem now i tought it was fin rot so i treat one of them to see if that did it and i lost him he was swimming upside down ??? now one of my fish has a cloudy eye wtf white cloudy eye please help i had them for over a year now i got when they were small see they mean allot to me