I recently added a clean up crew and I've started to notice that portions of my birdsnest coral are disappearing. Initially I thought maybe it was just the lower portion of the coral due to lack of light penetrating that far down. But I'm now noticing some of my hermit crabs on the coral and I just noticed spots that are exposed to the light disappearing. Are my hermit crabs eating the birdsnest polyps? Has anyone experienced this?