fin rot?

[proff1949]

The dorsal fin on my yellow tang is starting to look a little mangy. The distal edges of the fin have turned a couple of shades darker the the rest of him. Also the tail of my kole tang is starting to get the same appearance. Water parameters are all good. I tried to get a photo of these guys but details on the fins are not noticeable in a photo.

 

[Liberty]

If you still have the 50gal tank it to small for tangs. Poor things!