My astraea snails have not been doing well at all, they haven’t been moving really and at first I thought maybe they just have to get used to my tank as I just got them last week but my other snails are doing very well. For the past day or 2 they’ve been in the same spot but I do catch them moving slightly here and there so they’re not dead. When I picked up one of my astraea snails I turned it over to look inside and it didn’t look too good (as shown in picture) and when I felt the inside it was very hard. Does anyone know what this means or what I can do to help them?