My guess is that what you are seeing is skeleton that is poking through an area of recession or injury. Take that with a grain of salt though cause I don't have a ton of experience with these particular corals. That said it does look like exposed skeleton I have seen on other similar corals.
I have Cynarina which is similar and when it arrived there was some of this happening from shipping stress. Seller assured me that it’s normal when they are stressed to have skeleton poke through flesh and with good conditions it can heal in a few days. I target fed and it did heal in a few days.