Sick Montipora?

I'm interested in seeing what this is.

I just did a quick search and the only hints that come up are.
1- Montipora eating nudibranch which would be very tiny and found in the underside if the coral.
2- Another coral stung the Monti.

Can you see anything on it? Has another coral been close to it? Are perameters stable and in a good range? Can you think of anything that has changed in the tank over the last 3 weeks?
Could it be RTN? The only coral I've ever lost was a pink digitatus. It turned gray and half of it died a week after going into my tank. It turned white and then gray. I broke off the infected piece and saved the other half of the coral.

I'm new to reef keeping but hear are just a few questions off the top of my head.

Edited by LakeCityReefs - March 19 2014 at 9:54pm

Particles doesn't sound like bacteria. It sounds like something dropping from above. I've lost tons of coral for many different reasons. Thanks for the pic. From what I can see, these are the things I would look at:
Something dropping from above, like salt off the lights?
New lighting?
Salinity level?
Alkalinity level?
Calcium level?
Any changes in the tank up to 2 weeks before this began?
Answers to those questions will help figure it out and a pic of the entire tank could help.

Aloha,
Mark

Salt Creep falling down on it?

This is just off the top of my head but could it be spawning?