Need advise on shell shedding/mouldy on red ear slider!

[weiyan]

Hello fellow tortise lovers!
I've have two red ear sliders and one of them recently have its shell start to grow 'mould'. I'm not sure what it is but its a white layer of substance on the shell and layers of the shell seems to start 'shedding' off.
Please advise on what I could do to stop the condition to deteriorate and to treat it if possible!
I couldn't find vet that can help yet.
I thank you for your advise in advance!

 

[TechnoCheese]

I'm not entirely certain, but could it be shell rot? Can I see a picture of the entire enclosure?
Do the turtles have a spot out of the water with a heat lamp where they can bask?

 

[wellington]

They will shed layers of shell. It's probably that. @Anthony P can help you further.

 

[wellington]

Btw, do they have a proper sized aquarium or pond? They need a very large area as they will get very large. They should not be kept together and they need to get completely out of the water to bask under a UVB heat light and be able to dry out completely. They also need to be able to swim under water, so a proper depth is needed also. There is no plastic tote box big enough for them.