Do you feed your favia/acans? I feed 3-4x per a week due to my low nutrients (7-12ppm nitrate, 0.05ppm phosphate).
Also, what is the PAR reading where they are placed? I keep mine at 80-150 PAR and they are expanded/have their feeders out
EDIT: I don't think that it's due to fish nipping, otherwise other fleshy corals, like your candy canes, or your clam, would also be retracted