If any of your fish have fin rot, that is a sign that you have very poor water conditions. This will kill any fish in a tank eventually, so the first thing you need to focus on is what is going on with your water. It doesn't have to be just "clear", there are also lots of tiny invisible bacteria in your water that keep the water chemically clean, this is called "cycling". If you aren't familiar with this process, you need to take a look at the link below or the cycling stickies.