What is killing my snails?

[Wepwawet]

Ph 8.2-8.4
Ammonia 0
Nitrite 0
Nitrate 10

4 Black phantom tetra
5 Harlequins
1 Ghost shrimp
9 RCS

Back story got pond snails with some plants....... bam all dead. Bought some MTS mia never seen again. Bought 3 med sized nitrate<sp> snails one mia one with what looks like a a piece of the shell chipped off, one in perfect health.

Only have found 1 shell from dozens killed

 

[Autumnsky]

Don't feed for a couple of days and then when you have some time to watch your tank feed in the front only and you should see some serious action to the food. You may be able to get a better view and see your inhabitants.

If you did it in the evening, and turned your lights off until it was counting time you could possibly see even the MTS! I see mine when I feed, they are slow but seem to get there.

 

[Dreamwallaby]

I think low GH can cause the shells to erode, not enough calcium in the water. I added cuttle bone to my tanks to help that. Hopefully someone with more experience will answer.