I have noticed these "warts" on my favia from time to time. They seem to go away after a day or two, so I've never been concerned.
This morning it occurred to me that perhaps this is new polyps forming? The "warts" appear in different places, and never are there scars or other marks of injury. Other LPS seem to create a second mouth before the polyp divides, but I can not find any polyps with more than a single mouth on this favia.
If you look closely, you can see four of these forms. Anyone got the answer for me?