Ball anemones?

[miuYH]

Search up pseudocorynactis. They are not anemones but are more closely related to mushroom corals.

I have read that some are not vigorous eaters but some are. Some are harmless and some have reported missing fish because of these. I have one and I have never lost a fish but it is in a spot where fish doesn't swim there often.

https://www.youtube.com/watch?v=XYwcX6AVw5I @0:56 talks about the pseudocorynactis

Hope that helps...

Also if I may, from the pictures, it looks like yours are quite small so I don't think they are your culprit for your fish loss... but then again.. what do I know