Snail's shell is disintegrating

[aqua sapphire]

Abit of backstory as I'm a new owner of snails never had any experience with them. The pet shop sold it to me and said they were easy maintenance as long as you clean weekly. I had a betta fish for a year and decided to get a 10g to give him more room.

I recently got my snail about 3-4 weeks ago. I added him to a new tank along with my betta fish in a 10g. Prior to that I set up the water in the tank a few days earlier. My betta fish had some possible rot on his fin so I did a tetra fungus and bacteria removal in the tank. 4 days later I did a 25% water change and then another 25$ the day later and added the snail in. Snail was fine fast forward to a week ago I moved into a new place and did a 50% water change and cleaned up any fecal waste however 2 days ago I noticed my snail had alot of shell disintegration. I feed him cucumbers and salad. I added a cuttlebone to the tank along with some crushed egg shells as the pet shop told me my hardness along with calcium was insufficient. This morning I woke up and saw it didnt improve and was recommended by the pet shop to add a tiny pinch of baking soda in the tank as it's probably the ph. I'm going to go tomorrow and get a ph tester but my water is supposed to be in the higher 7 range. What should I do for now remove the snail from the tank and put him in a covered bowl with fresh water till the 10g is sorted out? I'm worried about his condition getting worse if I leave him in there. Here's a pic of what he looks like right now. He originally had a tiny bit of shell gone from his spiral point but now it's much worse.

Thanks for the help!

 

[aqua sapphire]

Also last two pics are of him the first 2 days just to compare the shell

 

[Autumnsky]

Did the fish store person test your water and tell you what the pH was?

It is pretty easy to make an adjustment when you have water with low pH. You can test and if your water is pretty acidic then you can set up your water changes to add calcium and maybe magnesium.

If you contact your local water supplier they will have a report which indicates the water quality, and get the information which will indicate if it is low on magnesium (other things).

It seems the snail might have been in more acidic water quality before you got him as well. And it is worsened now. People have put patches on a snail shell with a boiled /sanitized eggshell... and crazy glue gel.