Hey there! I corrected a few of the heads. The main issue I noticed is that, in most of them, the center line of the head was either too straight or didn't follow the shape of the head, making it look flat or crooked. By correcting this detail, the head has better volume, and consequently, the perspective improves as well. :) Keep the angle in mind, since in some cases (like the heads at the bottom), the eyebrow line and nose were diagonal and didn't follow the direction of the head's orientation. Sometimes it's helpful to think in terms of a box shape to maintain a consistent direction or perspective. Hope this helps!