At times yorkies do get flakey skin. But, what is more of a concern is that you were allowed to see them at 6 weeks of age, much to young for the public to see a new litter. The first 8 weeks of their life (until their first vaccinations) should be spend with mother and with interjected care of the breeder. Pups shouldn't be bathed until after their first vaccination about between 8 and 9 weeks of age.
However, there are some pups, yorkies as well as other breeds that have a condition called walking dandruff
Cheyletiellosis in Dogs (Walking Dandruff Mite)