Some sort of Nudibranch or Slug

Hey all... i have been noticing something weird about one of my corals for the past few weeks now, as it looks like it is slowly dying. All my other corals are doing fine and i wasnt sure what was going on, unitl this morning i saw what looked 2 me like a weird sea slug or nudibranch. It was moving along the glass, but on closer inspection, i realised that another 6-8 of the same thing were lying all over my coral and were slowly eating it away. One of my snails is also having a dig, and im going to have to try to trade them all in at the LFS for some credit, however i was wondering what kind of sea slug or nudibranch they are...

They are on the left and bottom right but blend into the coral well!!!

 

Not sure what kind they are but I'd get them out asap. They probably came into your tank on a rock or coral addition.

 

Do you think i should just throw them and the snail as well as the coral out? it is basically eaten..?

I dont know if my LFS will trade them, and the boss who i deal with doesnt get back until sunday?

 

If the coral is dead, I would toss it out. It's not looking too good in that picture that's for sure. You should also take caution in the future when buying from whatever store you got the infected coral/rock from