Is this shell rot or something else?

I have this baby res(about 1 month old) and he has these white patches on his shell. He had them since we bought him but I didn't think much of it until now cuz it seems the white patches have spread and worsened.

Also some parts of his scutes look kinda flaky/loose(red circle)

He's currently in a stock tub outside my house. The tub is mostly in the shade but occasionally gets some direct sunlight (I do water changes alot to combat algae)

I will admit he's very shy and spends alot of his time in the water and only basks if no one is near him.

I just want to know if it's shell rot or something else