Coral Beauty Problems

[alancolinet]

Hello everyone, I'm back with yet another problem.....my coral beauty has what I can only describe as fin rot I think..... the top fin ( dorsal fin ??? ) has 2 of it's spines COMPLETELY showing and it looks like it is slowly spreading down the rest of the fin towards the tail fin. It is a fleshy stark white around the area with a slight red coloing at the base. The fish seems fine and is eating normally BUT it is hard to not notice this erosion of the fin. Does this sound like fin rot??? And if so then how do I treat for it??? Slowly every day it is looking worse and worse....none of the other fish exhibit any signs of being sick and the water qualities are all in spec. I recently added some carbon in a 100 micron bag to help remove any of the possible water issues that there could be that I cannot test for. Any help or suggestions would be greatly appreciated since I am running out of time and I don't know how much longer this fish could have.