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