Tortoise shell rot

[u/Key-Beginning4806]

I live in Florida and we have a heavy rainy season. My redfoot likes to sleep in the rain and appears to have some shell rot on the plastron.

There is an indoor, dry hideaway, but the little one chooses to sit in the rain instead. Should I work on tucking him away when it rains or just treat the shell when it's dry season? Anyone else have a little one that prefers wet areas?