Shell Rot or Shedding - Spotted turtle?

[Ghazan]

Limited experience with spotted turtles, so not sure if this is typical shedding or shell rot. I have seen fungus on the skin, which this spotted does not have, skin seems fine. I noticed it when I dry docked her for 2 hours to do a water change.

Only reason why I ask is because I've never seen her go on her dry dock (she has 2 - zoomed floating dock and a sand area with basking light).

If shedding, just leave it or rub it with a brush?

Thanks.