General Care Discussion :: Turtle's shell is always white after long periods of basking

[Zacbuttcrack]

Why is this? This happens to both of my turtles.

Also, they both have shell discolourations. I tried brushing it off with lemon and vinegar but no luck. It's a sought of Olivey mucky green colour. This isn't the actual colour as bright yellow/green markings are present in certain areas of the shell.

[Diamondbacks4Life]

By any chance could you post a picture, could be a fungus or hard water deposits on the shell. I leaning towards its just hard water deposits because you say it doesnt appear till after long periods of basking.