My green scolymia brain coral has a black tip on one of it's tentacle bases. 2 other tips are showing signs of the same thing. Looks like the flesh has been stripped off of it for about 2mm.

Any ideas what it is? I'll try and get a pic of it up tomorrow.

The brains been eating portions of fine. It's next to a Scroll Coral and about 8 inches from a Frogspawn. Don't think they are the culprits though.