These are good academic studies, but there appear to be symmetry issues. I can see you're incorporating construction, and we know that's mandatory, but try to often step/move away from your drawings to see them as a whole, this shows how elements appear in relation to one another.
If you do "zoom out" then I say you need to do it more often, and rarely if ever get close to working on details. I judge that by seing the beatifully rendered details, but elements in relation one to another disrupt the depht of the form a tad.
Maybe drawing horizontal lines across the face during construction will benefit your constructing. Look here to see what I mean:
I took liberty and done some changes to your drawing. I hope you don't mind.
Except now the guy has too much shadow on his right eye looks like a bruise XD Again, hope you don't mind but I want to help you become better.