Is my Cowrie dead/dying?

I've had a 2 inch cowrie in my 75g tank for the last 2.5 months. he's been very active throughout the day. in the last 4 days, things have changed. first, i found him lying upside down. i righted him, but after a few hours he hadn't moved and it didn't look like his body was sticking out like usual. his mantle still is extended over the shell. i took him out to look a little, and his body moved around, so i put him on a rock. over the next two days, he seemed pretty active again, always moving, but staying just to one rock rather than all over the tank. then today he is again immobile, but now on inspection his body looks very shrunken inside the shell and didn't move at all. the only recent change is that about 5 days ago (the day before this started) i added 3 small turbos and 2 scarlet hermits to the tank. water chemistry hasn't changed at all.

anyone have any ideas what's happening? am i losing my cool snail?

tia

75g tank/ 20 gal sump. asm g1 skimmer, 110 lbs live rock, 8 snails, 2 hermits, 2 fire shrimp, 1 lawnmower blenny. amm,no2,no3 all 0, spg 1.023 to 1.024, ph 8.4, ca 390

 

Hopefully so. Has no place in reef tank...

 

omard, why is cowrie not a reef tank choice?

 

Open to debate...but most are carnivores. They will feed upon sponges, corals, anemones.


:-/

 

omard-thanks. dead cowrie is out of tank now - stinks too. fenner's book had said many cowries are good for reef tanks. i still can't tell if this one was in need of meat and starved or if something else was wrong. all parameters are ok, and the other 11 inverts and 1 fish look ok so far.