Mystery snail shell deterioration

[Ismene]

My snail’s apex has dissolved. I got her at the beginning of July. I don’t think it was this bad when I got her. Thing is, I know my Kh has been 5 or higher. My pH is consistently 7.4. I use remineralized RO water, so I test weekly.
Will it grow back? It has been like this for a month.
Also, will the growth line always be there? Or will her shell change?
She eats blanched zucchini & broccoli, algae wafers, Mineral Junkie pellets. There’s a piece of cuttlebone in the tank. I’ve given her a piece of TUMs twice.
pH 7.4
Kh 9
Gh 7

 

[Lucas35]

Not sure what caused it but it will not grow back. As long as it doesn't get to the point where the flesh is exposed it will be fine. The growth line will also always be their.

 

[Ismene]

Booooo, gotta buy them younger I guess.

 

[gorejusdesign]

Some of my mysteries are like that too. Like Lucas said it will not grow back