There are timews when you will notice a little more hair loss with yorkies -- not really shedding as much as hair loss just as we do. As Kazzy already identified, when the puppy coat is being lost to the adult coat is one of those times. Hormonal changes can also result in more hair loss -- female & thyroid hormonal changes are big hair loss triggers. Hypothyroidism can cause a GREAT DEAL of hair loss. So, if you see a lot, ask the vet about running a thyroid panel to include TSH, T4 and T3. You may also notice a little more hair loss when they go into heat, especially the first time. They may do it again, later in life. In general, if you notice a lot of hair loss in a yorkie, ask your vet about it.
The color changes of the hair on top of a yorkies head are amazing! It can come at any time and may change more than once or twice! My girl is 9 months old and her hair on top of her head has still not fully "broke" as they call the change in color. They go from black to silvery, almost white, to tan. Hopefully it will end on tan!
Yorkies hair color is one of the great entertainment and mysteries they hold for us. We watch for it, we speculate over it, we wish, hope, dread, and celebrate these changes in hair color -- ultimately wanting the blue and tan of breed perfection!