Hello all. My tank is a 50 cube with a sump. Most of my corals are doing well such as my hammer, Frogspawn, torch, and zoas. For some reason I am unable to keep Candy cane corals. I purchased a head and it began to recede. Thought I may have damaged it and purchased another and it appears to be going to same route. I don't have any fish which would possibly eat coral. Tested my tank and CA is at 400 alk at 10 and mag at 1260. Any ideas on what would cause this? Tank has been running for a year.