Yellow, scaly, flaky tail

Hi, back when I first started breeding rats, I let my older sister keep 2 females from the original first litter I ever had. I just got a call from her and she said that both of her rats tails turned yellow and scaly, and flakes are coming off them. It sounds severe. I have never heard of anything like this. The fact that BOTH of them have it leads me to believe its some sort of disease, as opposed to just dry skin. They are not being neglected in any way, she loves those things. Any thoughts?

My rats tails get yellow stained and may look scaly. She can try washing them to determine if the color lightens and the condition gets better, because its most often going to be gunk. If she thinks it's ring tail (a bacterial infection) she will need to get them in to the vet very quickly.

It's said that humidity below 40% can be harsh on their little tails. I would still get her to talk to a vet if nothing else.

Thanks alot Connie, I appreciate it.