My $.02... I have a couple scolymias one of which I nursed back from being nearly dead (purchased at my LFS for pennies on the dollar). I would guess I've had at least one scoly in my tanks for at least the past 6 or 7 years. The one I nursed back to health was actually worse than yours, although I am highly concerned that yours is on it's way out. Have you tried to feed it? My experience has been when they're as weak as yours they don't have the strength to exhibit a feeding response and therefore don't eat. If by chance you've not been feeding it, or it just won't eat try turning off all pumps while the tank is completely dark and drop some fine mysid shrimp or LPS pellets on the mouth area and check to make sure it has the opportunity to ingest some of the food for at least an hour (keep members of your CUC off of it) prior to turning the pumps back on. When I nursed mine back to health I fed it each and every day at 3 am for approximately a month. At first it didn't eat much at all, but eventually I got it to eat and once eating it healed rather rapidly over a 4-6 month period. Best of luck!
It is a meat coral acanthophyllia. Water perimeters, lighting or a fish picking at it. If you have a sump with lower light levels. Move it to sump. If it improves than it is either your lighting or a fish bothering it. Mine as been in my sump for over a year. Had same issues, found out it was my bi-color angel.
I thought mine was not issue. Until i placed it back into tank after it looked much better after short sump stay. 2 days later looked like crap again. Saw angel going for another LPS. Can't catch him easily easy to move corals.