I think the comments about the head have to do with the face not being big enough and improperly positioned on the skull. The back of the neck is also a tad thick and tends to give a visual impression of the face extending even further out from the skull than it does already.
ps: I had to compress the image more to upload it, I think after my liquify tweak you can see the point about face placement best on your far right figure (even if my execution is a tad sloppy). The head after the face adjustment could be enlarged slightly. I tried to adjust the face on the others but I’ve only got so much time to make a point