Light, you need more light. That is the primary thing amongst all three photos. They tend to be dark, and very flat. A little flash, and you will not only light up your subjects, but bring them out of the background.
Second, as previously mentioned, focus is off, that or you have really soft...
Stronger key lighting would help immensely. You really need to make the subject pop from the background, slightly underexposing the background can help with this, or just popping the strobe one stop higher as well.
As for the cropping, I agree with the others. Removing some leg would help...
I agree on the teeth thing, lotta yellows and oranges in there.
On the first one though, her upper lip needs to be lightened up a bit as it looks like she has a slight mustache due to the shadows.
But I'm a huge fan of the second shot, I love how the back light frames the face. Much bueno, IMO.