I think Zoe was 3 lbs 4 ounces at 16 weeks. She is now 7 months and weights 4.5 lbs. Her growth has slowed down alot in the last month or two. She has not gained at all in the last month. Although you have to remember that yorkies are like all of us, some grow at different rates than others. If you do a google search for "yorkie growth chart" you will find some charts that you can go by. Zoe followed those to the letter so it says she will be about 5.25 lbs. We shall see.
Also, I bathe Zoe about every 4-5 days but I don't think I've ever gone more than 10 days. I've used minksheen but honestly the best results I've had were with pantene human shampoo but I'm still trying to find a better one since I read that pantene is not the best for yorkies or people. Good luck!