Couple of issues here. First, are you sure the shrimp are truly Peppermint Shrimp? Camel Shrimp look very similar to Peppermints but are NOT reef safe.
Second, even Peppermint Shrimp are very opportunistic feeders and will certainly 'attack' a stressed coral or invert. Even if the coral or invert isn't sick or damaged in any way, they are definitely stressed after traveling from the LFS in a plastic bag, with poor water quality, put into new surroundings with unknown predators. Peppermint Shrimp seize these opportunities to munch on new additions, which is why I feel Peppermint Shrimp are the devil reincarnated. :sgrin:
Take an empty one liter soda bottle, cut off the top section (where the pouring spout is). Invert the top back into the bottom portion of the bottle, and secure the top with cable ties (zip ties) so it's like a funnel into the bottle. Put some food into the bottle, fill it with tank water, place it on the bottom of the tank, watch your Peppermint Shrimp walk right into it. I caught mine within 30 seconds.
Hope this helps,
Russ