HELP-dot dash butterfly sick

[RJaeger]

i've had it over a month now. last week i saw early signs of ich so i treated it right away and it cleared up within the next day.

yesterday i noticed it was missing a few little pieces of it's tail and now it's tail and fins are missing chunks. i thought maybe something was eating off of it but i haven't ever seen any other fish in the tank mess with it

 

[Amphiprion]

Can you provide some more information, like water parameters? Also, you can't necessarily discount fin nipping, as it can often happen while you aren't looking. Going up and watching the tank will often stop some behaviors, preventing you from seeing them, also. Any way to provide a pic? It makes it very difficult to make any assessment or give advice without some sort of guide.