Leroy's losing her color

[Purr]

Hi! I have red-eared slider, and she appears to be losing her nice green coloring on her shell. It's only up by her head, and it started off being when she came out of the water, and her shell dried, but now she looks funky even when she's in the water. Lester, her boyfriend (I think ) has it, too, but not as bad. She acts alright; she eats fine...I dunno what's wrong with her, or if she's supposed to look that way (?). I've never had turtles before these two, so I'm confused...I've had them for about a year, and this just happened recently. They've been eating the same food since I got them; Tetra-fauna floating turtle sticks.

Is there a turtle person out there, who knows what wrong with my scalie girl?? Thankz!!