Help! Fish disease?

[jennytheleopardgrouper]

Hi everyone, I've been uber-busy and haven't posted in ages. However, I need some advise. My squarespot anthias, which has always been very friendly and outgoing, started hiding and not eating a week ago. I finally caught him and checked him out and he's got a huge swollen eye. Now I just realised that my Coral Beauty is hiding, and has holes in his tail. And since this morning, my Sailfin Tang seems to be missing, no where to be seen. I assume this is a disease. Any thoughts on treatments? I have a quarantine tank I can treat the affected fish in. There have been no new additions for months. The only problem in the recent past (although pretty bad), was that I accidently turned my heater off 2 weeks ago. The tank got down to 75. I lost my blue star a couple days ago, which I assume was due to this. My baby regal tang has also been a little terror lately, chasing all dark or similar coloured fish.
I did 2 water changes this and last week in case there was some sort of contamination, but this didn't help.

Any help would be greatly appreciated. Thanks!