Congratulations on your beautiful babies!!!! I am so glad to hear that all went well with the whelp.
I was surprised when you were describing the birth order and hearing the mention of chocolates. You originally mentioned mama was a silky bred to a Yorkie, correct? You didn't mention her was a chocolate yorkie so I assume(d) the stud was a traditional. If that is correct, then there must be the chocolate gene in the line somewhere; I'm not sure on the whens & how the genes show themselves in litters though???
Nor do I know if that color is possible to come from the Silky breed either. As far as the chocolate color goes; it's just one of the varieties of Yorkies like the partis, goldens, etc. Not of the Yorkie standard, but nothing wrong with them health-wise that I know of.
Good luck with your litter; can't wait to watch them grow.