Yellow Tang missing tail

[pm64971]

Hi all,
I seem to have a problem with my yellow tang.
My tank has been established for about 2 years and my yellow tang has been a part of it for nearly the entire duration.
I noticed today that she is missing all her tail fin. All she has left is a stump. I think this happened in the last few hours. I'm not sure what to do with her or to help her.
Anybody have any thoughts about the cause or what I should do?
Thanks,
Phil

 

[melosu58]

I `ve never seen that before. Something had to remove it either a tank mate or disease. Check your water params