SPS frag swelling??????

[fishoholic]

I got this sps frag on Sunday and it seems to be swelling up on one branch. I have no idea what that means or why it's doing that. All my other sps corals seem fine. I do have small flat worms in that tank so I'm not sure if they could be the cause or not, as a far as I know (a friend told me) that they were the harmless kind, but I'm not too sure. Any ideas?

Before pic. (4 days ago) circled area in question


After pic. (today)