There are a lot of good volumes in there! Well done!
If was being picky I would say your lips on the first head appear kind of flat. I find that shading lips as if they were cylinders gives really good results (I would attempt a paint over but I'm at work and cant get to a tablet). The same issue with the chin in the first head. where the light hits on the left, its reading as either flat or slightly off (this may be because the second light source hitting the right side of the jaw makes the values slightly awkward to work with).
Other than that though these are very good! The features are well proportioned and your values are great! Keep it up!