The discolouration is likely perfectly natural. You can generally easily see it on a dog’s belly that is not fur covered. The fact that they have been shaved is about as natural as breeding miniature “toy” dogs. You shaved them looking to see if they had a skin condition and then don’t know anything about skin conditions?

How about shaving your childrens heads to make sure they don’t have headlice?

A rash would be as obvious as on a human or any animal along with the discomfort of the animal.

the best advise anyone can give you is to ask your vet about it. the only way to know for sure is for your vet to determine if it is a problem or not.

Not a rash, my JRT is covered with spots like that and he is white bodied. It’s just the pigment in the skin.