I recognize a little something that's a problem for myself and a certain other member around here: the dreaded slant. It often happens to artists who have grown used to drawing not on a desk or easel or something stable, or in your case your tablet might be slightly slanted as you draw. It's especially prominent on the first.
Thankfully, that's a pretty easy fix, so long as you keep an eye on it. I can't really complain about anything else at the moment, although I question if the eye on the second image (the headshot) was meant to be slightly closed for a facial expression or if you simply use straight lines to guide where you place the eyes?