your representations of heads are lacking fundementals. Stan Prokopenko also made a course about portraits, there you can learn the loomis head method (wich is easy and accurate, almost everyone uses it)

Those are some pretty good drawings, you generally match the energy/flow. But there are some things which aren't correct. (at least I think). In some poses the sterno will be stretched. For example, in the last picture, you drew the sterno in a smooth flow, but it will actually be stretched. Also, in general, you can draw the levator a lot bigger at the clavicle. It will usually take up half the space. Lastly, your trapizius can go bit futher on the head, and remember that that part will follow the flow of the spine.

your scapula is a bit too small, but the foreshortening is verry well done