1: I think the previous posts have already described your whites enough. What I noticed in this image right away and it held through with the others is that you need to pay a bit more attention to your background. Having unflattering/random elements back there can really break down what would have otherwise been a great shot. Some of the suggestions brucer007 gave for changing this first one are a great place to start.
2: personally, I didn't notice the crotch so much. I was really interested in the facial expression on her and the rest of her positioning. Once again please pay attention to the background, that wall outlet on the right is distracting since it looks like she's staring right at that.
3. As was already said, it's blurry and an unflattering color. Really play with the white balance controls on your camera so you can see what it does in different situations. The best way to learn how to use your camera and get better at it is just to shoot over and over and over.
I did want to mention one thing that I really liked: I really liked the poses your models were in. It doesn't matter to me if you actively told them to pose like that or if you just chose those as the ones you wanted to highlight in this post. Either way, I think you have an eye for that. Play with that more and you'll start to make your images even better. There are a lot of people who can take technically great images (white balance, lighting, and colors are all right) but if it's a boring pose the image is going to be boring. I don't think that's going to be a problem for you.