Brittlestars and tissue loss at base of my acro?

[pochaxoo]

I noticed this tissue whitening on the base of one of my acros on the shadded side of this coral. I see some brittlestars here but want some advice on whether they are just feeding on dead tissue and should I be re-fragging this piece to prevent spread of the tissue loss?

 

[TaylorP78]

The brittle starts are just eating the dead tissue, but is the skin just whitening or is it receding