Is there something hurting my coral?

[Sonam]

Not sure why our blastomussa is looking this bad. It contracts at night normally but there seems to be something on it? Is it a problem? We've had this coral for probably 3 or 4 years.

 

[Bouncingsoul39]

Maybe a fish is nipping it? Also, I see some stringy white stuff in the center of the second pic. Not sure what it is, but maybe it is irritating the coral. You try very carefully removing it with some tweezers.

 

[Sonam]

Thank you for your response. I dipped the coral and the stringy stuff was removed. It seems to have recovered from that but it keeps getting irritated.
We have some emerald crabs that are fairly large that hang out around it. I'm wondering if that is what is causing the distress. Or our yellow angle fish. That fish has grown large.