When I first got into the hobby, I was always adding different types of supplements - calcium, iodine, strontium, etc.. The problem was that I was not measuring for any of these things. Things seemed great for a while and then it crashed - most of my coral died including the xenia I had.
I learned from those mistakes - now I do not add any supplements. I have been relying on a 10% weekly water change to replace whatever has been used up. As a result, my xenia has been spreading along with the other corals in the tank.
Stop adding calcium unless you are testing for it (and anything else for that matter). Keep up with weekly water changes - with a little time, everything should be fine. Whatever you do - don't rush anything. Somewhere on this forum, someone once said "nothing good happens quickly in a reef tank" - words to follow.
Kevin