I agree with the previous poster - the 3rd shot in the first set is great. The lighting is nice - and the shadows are nicely (strategically) placed. The light in the first shot doesn't bother me, but I don't think the angle is all that flattering - her legs look a bit large. Girl #2, with her being upright, would've looked more natural with her knees place a bit further apart.
In the 2nd set, the first picture is nice, but not at all fitting with the rest. I'm guessing she wasn't comfortable at all. The second shot is good - but the positioning of her body doesn't look natural or comfortable. While I appreciate the modesty of keeping her knees together since she's sitting down (thank you!), it might have looked more natural to let her sit more comfortably and shoot her from the side.
Most of these issues have more to do with the subjects than with you, I think. Were these taken toward the beginning of the session?