Love your photos Michele
There is no standard to the height for Yorkies, just weight between 4-7 lbs so you will see lots of different heights in the same ring. If you get a chance to see the DVD of the National Specialty in NY you'll see what I mean- lots of beautiful dogs ranging considerably in height and proportions. Different people like different types. You could have a very tall dog that could weigh only 6 lbs because he is light in bone, or a short dog with lots of bone that could weigh between 6 and 7 lbs. Not saying that anything is right or wrong, but you'll notice that different judges like different types.
My Sebastien is 9 1/2 " and weighs 5 1/2 lbs. He has medium bone and is average build- not slim or chunky. I really like his proportions. I noticed that in NY he was on the smaller size, there were many tall dogs there
Here is a photo of him next to some other dogs in NY last year, you can see the difference in size