Peppermint shrimp are evil. After having my peppermint shrimp for many months they decided one day to start eating all my mini-maxi anemones, then they moved on to LPS. It makes no difference how often you feed them, some just go rouge. These were not camel shrimp. Peppermint sometimes just become opportunistic feeders. Look around on forums, there are tons of reports of peppermints shrimp eating LPS.
My peppermint shrimp ate acans and blastos, so I moved them to a fish-only tank. Remember that these shrimp eat a variety of things, including anemones. If they find something edible, they will go for it.