Some of the poses are bending foward and you seem to have drawn them stretching backward (the 2 from Yoni and that one from Laura) look for folds in the belly if you are having trouble understending the direction the torso and hips are going. Also, try to look for the underlying structure and gesture of the trunk, not the other body parts. In that last drawing of Sekaa she is fully bending backward, but the action lines of her neck, arms and breasts can make it seem like her torso is curving upwards halfway through. The movement of the neck and arms do not affect the underlying structure of the torso

You are having trouble tracing the central line on the contour of the face, the moment you start adding the features the portrait is going to look very squished and off center. The bottom right loomis head is the only one you actually got right, try and replicate it on your next heads.