Turbo snail help

Good afternoon everyone. I have a new tank set up. Dec 30, 2017. All parameters checked weekly. Once established I added 1 turbo snail and 2 blue legged crabs. All was good. Had abloom of an orangy/ brown algae. Vacuumed, 30%. Parameters still good. Added 1 more turbo snail 2 weeks ago. Everything still good. Added a banded goby 3 days ago. The snails are closed and wont open. Not sure if they are dead. Picked them up and smelled them . They are pretty smelly so I set up a separate tank for them and put them in it. Still no movement. Any suggestions? Thanks