Silk tonga mushroom melting?

[Pat02026]

Since yesterday I seem to have a few mushrooms melting away. Have these been known to do this, and is it likely that the rest of them are going to do the same thing? I would say 3 out of 10 have done this. No other signs of stress or issues with any other corals.

There's nothing around them that could have upset them except for some Xenia and I would think they would outcompete the Xenia;