Thanks very much for the quick response.
Here's a photo of the guy. He was one of my "test" fish and I really like the little mutt. I guess he's been here from the start of my folleys...
Anyway, you can see in the photo the rot on the fin as well as the white on his tail fin. Since last night it's improved dramatically. He did have a few white spots on his body that seem to have cleared up already. I may have hit the panic button a little too hard here, but better safe than sorry.
I do a 10% water change religiously each week. Added an airstone last night to increase the oxygen. (just got lucky here... trying the common sense approach) Anyway, thanks for your help again.
Grant