What's up with this acro?

[SKremk]

I came home today and found this acro frag looking bad. Both the coral flesh and the polyps on several of the branches are swollen and inflated. There is also some sort of wound on this branch, either a bite, or where the swollen flesh has 'popped'. I've looked for parasites and don't see any, and everything else in the tank looks ok. The frag isn't near anything that could be stinging it. Has anyone ever seen anything like this before? There is no RTN actually happening, as far as I can tell. All the flesh is still on the coral, it's just all puffy. I've had the frag since October and it has otherwise been healthy. Any ideas?

SG 1.024
Temp 77
Cal 420
Alk 9.6
Mag 1180
Nitrates 5
Phosphate 0

http://i53.photobucket.com/albums/g71/skremkau/IMG_1433cropped.jpg

[chefzif]

Looks like a crab clawed the acro? IMO

[BuckeyeTodd]

Looks like something took a chunk. You have any big angels?

[SKremk]

I've got a Potter's Angle but I've never seen him nip at my SPS before, and I've had him a few years. And I've never seen a acro swell up like that before. Several of the branches are puffed up like an LPS.

[Acronic]

That is a normal reaction of stress, I wouldn't worry too much