New snails have not moved in 4 days

[ianryd]

I got a batch of snails from Denver Reefstock on 3-8. Most are doing fine, but there are a Turbo and a Margarita (?) that are just sitting there. I checked if they're alive this morning and they are, but they literally haven't moved an inch. I temp matched and drip acclimated them for 30 minutes before dropping them in the tank. They are foot side down, just fully in their shells. Should I be worried? When should I pull them if it comes to that?
Latest parameters are
Temp 77.5
Nitrate 2.5
Phos .05
Salinity 1.027
Cal 411
Mag 1290 (I added a little after this test so it's probably more like 1320 now)