I have the same problem!
Will8,
My colt coral is currently undergoing the same problem! It was acting fine but then unfortunately one day just a few days ago it was discolored and shrunken considerably! It looks very similar to the picture of yours!
My water statistics were very similiar to yours as well. The only thing that I noticed was perhaps your Alkalinity was a bit high? but Im not an advanced aquarist by any means so I could be wrong. Still all in all your water quality seems good to me?
I did some research on the issue because I have a clownfish that lives in my colt coral and he is very stressed since this happened, so Im trying to resolve this issue ASAP. I asked my dealer and he said sometimes that Colt Corals will do this for a few days. He said it is "normal every now and then". I poked around online a bit to see if there was any truth to this, and found someone else who had made an article with the same problem. He thought the coral was dead for sure, but after almost 5 weeks the coral sprang back to life just as before! So apparently this cycle can take a number of days or weeks?
Im hoping that both of our corals are just going through the same odd cycle. My advice would be to just stay on top of your current water conditions and dont give up! I'll be doing the same!
FireFish36