Can you post your current water parameters? temp, salinity, ph
How long did you acclimate the snails when you first added them?
Did they ever move/eat at all?
Do you have lots of algae in the tank? Turbos require a lot of algae to live.
Any of the following reasons could cause a snails death:
- Too short of an acclimation period
- traces of copper
- low salinity
- salinity swings
- temp swings
- starvation