I was going to say, it looks like you’re sculpting the same head over and over
Definitely some progress in quality, and I’d imagine speed behind the scenes. I’m not seeing any obvious areas for improvement with this latest one beyond detailing.
I also tend to gravitate toward facial appearances that are very similar to one another. One way to break out of that may be to over/under-exaggerate features you normally do not for characterization. For instance, so far you’ve sculpted wide noses, prominent lips, cheekbones, and brows. For a few heads, choose one feature and make it purposely dissimilar (say, thin lips), sketch that in, and make the rest of the head work with it. If you’re like me, everything will look wrong at first, and you’ll have to struggle to avoid returning to your ‘safe zone’. Once you have some feature differences sculpted, pick and choose random ones and do emotion studies. Then perhaps some likeness studies. You’ve shown your workflow – try to use a different one entirely and see what it does to your sculpts.
Of course, I say all this, and I’ve never tried to do it myself, so… it is what it is. 