I would shoot tighter, closer. The first one she looks a bit slouched in posture. I would work on posing them keeping in mind the formal rules but also giving them leeway to relax into the poses. Her right shoulder should be turned to the right a bit more so you are not looking at the shadow of her back. Sit up straight, chest out a bit, shoulders back a bit more, and just rotate those shoulders so that it doesn't look like she was walking down the street, turned in your direction and you snapped a photo. I agree about watching out for bright highlights. You want to balance the hair light a bit more with the key light. Also, in the third photo the girl's hair should not be covering her face when she's looking down.
In regard to composition, use the rule of thirds a bit more. You are shooting straight on as if your camera is stuck to a tripod. Move around a bit and find a more dynamic perspective such as a bit more from below. Make the lines in the frame in the background diagonal instead of just straight across and up and down. That places the models in this static environment...it is a nice frame yes but you also want the models to not seem confined by the structure behind them.
The second one could be a 3/4 or half view rather than full length but if full length then I would fill the frame more with the model.