My superman does that when I accidentally drip kalk paste on it. I've always taken it to mean that they're really, really upset about something because that's the only time I see it. They have always recovered just fine.
Ditto. He is disgruntled by something, and spewing his guts out his mouth. Lol. Generally, they recover fine though. It’s shocking at first, but something everybody sees sooner or later.
Peppermint shrimp, and camel shrimp, are both susceptible to this behavior. If so, they will completely annihilate the mushroom in a matter of minutes.