Your braincase looks a bit on the small side. Give it a bit more bulk and lower the position of the eye sockets on these and the proportions will be more accurate. Keep up the sketching 👍

I like drawing skulls too. The second and third skulls look fine to my eye, but it's the first one that has some issues. The thing that stands out most is that the nose cavity is shifted to the left. Also, from the eye cavities to the top of the head we see a level skull, but from the eye cavities down (except for the nose cavities) the skull is tilted to the left. You can use lightly drawn or imaginary horizontal and vertical lines to make sure features line up with other features on the model at whatever angle it is being viewed from.