Overall these are very pleasant to look at. But I agree with Benshogia that the pose is really awkward. You can get away with the gunslingery arms, but the legs completely alienate me because I can't fathom why anyone would stand like that.
You also pillowshade/band a lot. This becomes evident when you look at the brim of the red hat. I spent a few minutes on each of these heads where all I did was clean up the banding. It's really fast to fix and makes them look loads better because they're more defined and are less amoeba. It's present in a lot of places but I'm sure once you become aware of it you'll have no problem fixing them up much better than I have.
I think your best hair is the brown hair in the middle of the top row, because it isn't weak and pillowy and clumps of hair are semi-defined. Do more like that!
The poofy <3 pants as seen in the second row might need some attention as well.