Don't necessarily know how make it better, however, I see a lot of oversimplification on the nose. Try this out again, but by blocking out all the shapes. This should give you a better understanding of how the plains of the head are, and will make your simplification far better.
For example, your second head shows a decent understanding of a noses underside. The face to the left of the last one, shows it poorly.
All in all, my advice would be to practice a more complex shape of the head, then take traits from it and boom; you'll have better simplified heads. Hope this is helpful!
