Help my baby red ear sliders shell is turning white!?

I have two baby red ear sliders and this past Friday i cleaned there tank. I clean there tank once a week but when i cleaned it this time i had bought them a new fake plant so they could hide if they wanted to, then the next day i notice one of my red ear sliders shell had white patches on its shell like if it had water or something under its shell. I was wondering if it shedding its shell or if its fungus. It does not smell but i just want to make sure. I give them all they need, a landing dock, uvb/uv light and i make sure the water is the right temp so i dont get how it would get sick??/