Turtle shell

[wally3218]

I discovered these black marks on my murray river turtle‘s shell and what looks to be shell skin coming off. Can anyone tell me what’s happening and what i should do.
thank you.

 

[spider2.0]

It's shedding the scutes on its shell
And the black is just algae that was growing on the old scutes which haven't came of yet and the other coloured bits are the new scutes perfectly normal and healthy just like a snake or lizard shedding their skin as they grow