Snails keep dying?

So I've had my tank running almost 2 years now and for some reason I can't keep snails alive. I will buy a batch of snails and most of them will die off pretty quickly a few might live a month or two but then are toast. My fish, starfish, shrimps, conchs etc etc are all doing great. Water params are all in check so I'm confused. My hermits seem to have the same issue as well. I have like 2 or 3 hermits in my 180g and 1 snail.



Anyone have any ideas what might be causing this?