If it was copper, I would be very careful when I used the rock that's currently in your tank now. I had a genious moment when I added a copper fitting to my sump soon after I joined the hobby. All snails, crabs, shrimp, corals, and a few fish died. I too had some xenia and it looked very much like yours shortly after the contamination. Although I didn't have any SPS at that time, I specifically remember black spots on one of my finger leathers as well. I also had "globs" of film on the top of the water that I was told was the bacteria die off.
Do yourself a favor and test your water from copper and at least eliminate or confirm that as a cause.
Although I discarded all rock/sand/coral skeletons after this happened to me, I'm still in the hobby with a tank that's thriving. It gets better...
God bless,
Chris