You need to get models more relaxed. They have a neutral expression. Also, even though it is your most viewed picture (and I must admit I clicked on it), I would get rid of the crouch shot. It doesn't enhance your port. Keep post!
You're right that the models weren't relaxed enough - they were both very inexperienced. (But great girls!) But what's really interesting is that I have much more range of expression from both of them, and I chose the neutral ones. Wonder what that says about me...
Get yourself a full spectrum light bulb. Nothing says "doing it on the cheap" like the cool window light on one side of the model, and warm incandescent bulb for fill light. Either match the light or bounce the light, but drawing the viewer's attention to how you lit and away from what you are lighting is always a negative.