Sounds like a bacterial infection to me. Interpet are a good brand, and I have used their meds before to treat thos problem myself previously.
Other than that, things don't look too bad. The bad news is though, that the anti-internal bactirial meds will slow the cycle

Nothing much to be done though....Unfortunately, whatever med you use though, the fish showing loss of colour and large bellies, probibly can't be saved, so you may need to consider euthanisation on them. The one with a blister though, should be curable
More recent problems, such as this, usualy attract a better responce, with their own thread BTW, so next time, if you open a new topic for these issues, you may get help more quickly
All the best
Rabbut