Fin Rot or something else?

[rcbc3384]

A question
What is Fin Rot? So far 3 fish in my tank (a Blue Tang, a Yellow Tang and a Pecula Clown) are experiencing fins that seem to be eaten away (Not crazy amounts but noticable) All of my levels were good except pH was low but after some Buff the tank is ok. This is a community tank so I'm a bit puzzled.
Any thoughts?

PS: pH is still low as of just now (7.9)

 

[ufchristyb]

Is there an aggressive fish in your tank? How are your other levels? Any issues with ammonia?

Got any pics of it?

--Christy

 

[Steven Pro]

Fin erosion is sometimes one of the early signs of Marine Head & Lateral Line Erosion, especially considering low pH (i.e. water quality issues) seem to be a contributing factor.