Hi! Your portraits are beautiful! You have a very solid grasp on expressions and general anatomy, especially with the eyes like Jeannethornton said. I think that you could just spend a little more time analyzing the specific shapes in the faces of your references to pull it all together and fully understand how different faces break down geometrically.
I would actually reccomend using tracing as an exercise, so you can really analyze the shapes of the face. This is how I use tracing: I use my laptop w/ my ref photo underneath my paper on full brightness, so it shines through the paper, and then I spend 5 mins breaking down the shapes of the face like the eyes, mouth shapes, etc. Then, I take out my laptop from under the paper and spend 5 mins drawing the ref w/out tracing. Finally, I put the sketch I made w/out tracing overtop of the laptop w/ the ref like before to dissect the differences between the photo and what I put down on paper. I find I can see more clearly if the jaw was too big, or if the eyes were way to far apart, than if I was just looking side-by-side.
Hope this helps!
