On and off lurker over the years but first time posting. 9 yr old 90 gallon mixed reef. Lost two of my original fish (hawkfish and flame angel) that we purchased February 2012 and am in the process of restocking fish and adding a few more corals. I ended up having to move my Zoa frag I added as my bta decided to do a walk a bout and now it has some greyish stuff around the edge. I’m hoping this is the normal stuff that happens when you piss off a coral but suggestions are appreciated. Thanks!