shroom puked up guts?

I've got a fuzzy mushroom that's about 7" on a rock with 4 other smaller ones. He's been in the tank for about 2 months or so and he's been doing great. Last night, I was watching the tank and he spit out his insides? I did a bit of research and found that this seems to be somewhat common, but could not find a definative answer as to why. All other corals are thriving and seem to be doing great (well....my xenia aren't pulsing, but I'll put that in another thread)

He's pulled them all back inside and seems to be doing fine now.

So, my questions are: Why do they do that, and Is this something I should be worried about?
 
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