Tank Temperature and correlation with snails dying?

So I bought a cleaning crew and they have slowly died off over the past 5-6 months. Originally I though it was my on blue legged hermit killing them all one by one. After some research I saw most snails cannot survive long periods of times in higher temps. I keep my tank right around 80 degrees and wondering if that's why they have slowly died off. I ready astrea snails can survive higher temps and they are still alive. I lost my mexican turbo, ceriths, and some other types. Any info? Should I lower my temp, or mostly only keep astrea snails. I still have a ton of limpets.