Looks like an upset S. haddoni.
Symptoms do appear to be coral injury, but they also consistent with some level of predation. If it continues to show distress and or the size of the affected area increases, assume a predator since it does not appear to be in an area with aggressive coral.
Make sure it is getting some flow to wash away heavy sliming and prevent bacteria growth. Also, make sure it is not getting kalk, or other supplements dropped on it, touching heaters, etc.
fwiw: typical predators, cowrie snails, eunice worms, shrimp, fish, etc.