Whodunit !?!

[SAMSHUNG]

Recently put in an Aussie Acans that I'd waited forever and a day to receive. Few days in and it appears it's being consumed (like seriously eaten up) by one of the tank inhabitants. This is only happening at night as I have my tank next to me nearly all day and haven't witnessed anything come close to it. Therefore I can pretty much eliminate most of my fish from being the culprit as they're busy sleeping. But i'll mention all the tank inhabitants anyway.

1 Peppermint Shrimp (I suspect it's her)
2 Cleaner Shrimp
3 False Perc Clowns
1 Foxface
1 Hippo Tang
1 Royal Gramma
1 Dragon Goby (doesn't eat ANYTHING let alone coral)