I have been running my system for a year now at the beginning I only have several single mushrooms which have gracefully multiply. My problem is that, I started to add other corals now that the system is old enough.

So far I have:

mushrooms
hairy
Rhodactis
green montipora
zoos
palys
pink birds nest
gsp

also:

3 bumble bee shrimp (one carrying eggs)
1 porcelain crabs
5 turbos
3 nassarius
and one lonely six line wrasse.

Before I had a toadstool that was like 8 inches across and it died in like two weeks, something was eating it from the inside out. Now I purchased a colt coral to try it and it seems is happening again. My guess is a parasite. All corals are separated from each other but still as far as I know there is no aggressive corals on that list.

Does anybody know what this might be? Has it happened to you?
Any ideas

Need the tank specifics the regular routine, could be bacterial could be nudibranch or lights. Sorry if I missed these items. And a pic would help.