Bowser and thinning shell

[Bowser2017]

Need help
On the right part of his shell is thinking or it’s white and flaky just in the crevices. What is happening?

 

[Bowser2017]

Should say thining

 

[ascott]

Need help
On the right part of his shell is thinking or it’s white and flaky just in the crevices. What is happening?
View attachment 266526
View attachment 266527

Looks like and injury. Have you soaked the tort and then gently brushed with a soft brush (soft toothbrush?) and then watched to see if that appeared again?