I have a 30g tank that's been set up for almost a year now. i have a clown fish, yellow tang, coral beauty angelfish, and a six-lined wrasse. my fish all get along for the most part but for the last few weeks i've noticed that my yellow tang's fins and tail are getting more and more frayed and now it looks like it's starting to happen to my coral beauty as well but it's not as bad. could anyone tell me what might be wrong? unfortunately, i have yet to test my water parameters, but i did do a water change about two weeks ago and everything has been fine up until now? any help would be great. thanks.