I have 3 snails in my saltwater tank. Recently 1 of them flipped over and hasn’t moved since. I flipped it flat so it wasn’t upside down and still hasn’t moved. Then yesterday another one went upside down, I flipped it and it hasn’t moved. Should I assume they are dead? I don’t want to take them out because I’m scared they might still be alive, but I also don’t want to put the tank at risk for leaving something dead inside.