Fly 75,
Fin rot and cloudy eyes can be related, AND they are commonly caused by three different problems. Can you post a picture? If not, can any of the fish be captured? If you can do that, you might want to try a freshwater diagnostic dip to rule out flukes. To do this, you place one of the fish in tap water that is the same temperature as the tank (some people also adjust the pH of the tap water, but I never bother to do that). After five minutes, return the fish to the tank. Using a magnifying glass, look at the bottom of the dip container. Anything that looks like a worm is suspected of being a fluke - seeing more than about 10 of them in a dip indicates that is the cause of the problem. If you can see the dropped worms with your naked eye (they look like the fish's scales have fallen off) the fish has Neobenedinia - a different type of fluke.
The second possibility is that the fish have Cryptocaryon (saltwater ich) that has progressed past the white spot stage and become more diffuse. I don't mean to insult you by thinking you could have missed ich on your fish for the past week or so before it got to this stage, but it can happen.
The third possibility is that the fish have bacterial infections. I find it difficult to believe though, that a whole tank of fish would come down with a virulent bacterial infection with no predisposing factor - that really just doesn't happen.
There are some other disease issues that could cause similar symptoms, but they are rarer.
It would also help if you posted a complete history - water quality parameters, how long the fish have been in the tank, when was the last one added, etc.
JHemdal