Rhodactis Mushroom vs zoanthid question
 

I am missing one of my newer zoa frags and my largish shroom that is generaly underneath them has 3 big ulcers where its mouth used to be?
i ripped all my easy rockwork apart looking for the frag and could not find it and while doing that noticed the holes.

would the zoanthids do that?

Zoanthids are very toxic, so it is possible. Rhodactis mushrooms form a vase at night to trap and eat fish so it's possible but unlikely that the mushroom consumed the zoanthid (or Palythoa). Are you sure they are ulcers and not fission splitting?