what did this??? bugs???

i had a piece of coral that wasn't doing so hot for me (blue digi)  i tried to mout it on a different plug, and well a snail broke it off, i thought it was done for anyways so i let it sit on the floor of the tank for a bit.  the next couple days i started to notice a little bit of extension around the base, so i thought it might be coming back so i just left it there.  well i picked it up today to check on it and possibly move it to a better place and noticed some little critters on it.  also noticed what you see in the pics too. they may have been there before to i dont remember  i just thought it was dieing there, but it seems to be eaten.  i'm not sure on the little bugs i saw, they weren't pods as the seemed to crawl on the coral not move. i checked out a few other pieces and i'm noticing some tissue loss on my orange digi.  green digi seems to be ok, but some of it dont have very good extension.  could it be nubibranches or red bugs????  i lifted up my brain that sits on the floor of the tank and it seemed ok...


oh i did remove the piece from the tank completely and i removed all other little pieces that were on the floor of the tank.

 

everything checks out right cept my phosphates are a little high and i think thats cause i was using tap water. i'm using RO water now and doing slow 5 gallon water changes every other day but not sure what the critters were that were on the piece though, they weren't pods as they didn't swim they crawled