Declining Discus

I have a 65 gallon with 6 discus and one angelfish. Fluval FX4 filter, light gravel on the bottom, temp at 88. 4 of the 6 discus are growing,fat, thriving and 2 of them have developed multiple issues. Their fins are rotting off and they are losing weight. They are still active and eating normal. As of the last couple days their gills are red and inflamed. I have tried API general cure, melafix, kanoplex. The fin rot seems to hault while the medications are being used but as soon as they are stopped the progression continues. Let me know if any additional info is needed, I’ve tried everything I know and nothing is solving the problem.

There's a questionnaire that you should probably fill out it's a sticky on the Disease/Sickness forum.

In general the first question you're going to get though is what is your water change schedule?

Thanks, Tony. Les 7208, when you fill out the form please include pics of the fish that are not doing well as well as a whole tank shot. We love to help, but you have given us little information to work with.