I think you have drawing the contours down pretty pat.
There's no mass/ form indications in the drawings though. It would be very hard to improve how you are reading the contours with more time; maybe try to include the basic masses/ forms in the longer gestures.
I would say my feeling is there's just generally "coloring book syndrome" where tones can be added, yet without them effecting/ informing the contour. Its always a struggle for me not to draw a figure and then "shade it in" off the outline only.
Maybe try the side of a piece of charcoal versus the tip across the figure so form is "built in" more
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