Fleshy bubble on my red planet

[Keithcorals]

I've got over a hundred SPS in my system and had a milli frag do the same thing a week or so latter it just went away. I do t have a clue what causes it but it seems sort of random.

This is my red planet that is is in the same tank as the milli that got the bubble

 

[Mike&Terry]

I've seen coral do that when mag was too high.