I bought 12 nerite snails for my 10gal which has been cycled. Current water readings are 0 ammonia 0 nitrite 10ppm nitrate. I've had these snails for about a month now. I know when they fall off the glass they are able to quickly flip themselves over and continue on. Yesterday I noticed one snail on its back not able to flip itself over. I helped it out by physically putting it upright, but it flipped itself over on its back right away. I did this a few more times and it just kept instantly flipping itself over onto its back. I took it out of the tank and placed it in a plastic container with barely enough water just to keep it wet. The snail was able to stay upright and explore the container no problem. I left it in the container overnight to give it some time to recover from the fatigue. Today I placed it back in the tank and it just keeps flipping itself onto its back again. What can possibly cause this behavior? Almost like the pressure of deeper water is causing the struggle to stay upright. I feed the snails algae wafers and veggie wafers. Any insight is appreciated.