Click on thumbnail to see larger photo.

There is nothing much wrong with the first picture; the bow is probably a bit too close to the fingerboard.

In the second, however, the hand and wrist has rotated a bit, pulling the little finger up on top of the bow, and dropping the index finger too far over the stick. Also, the elbow looks to be rather straight, with the bow this close to the frog.

The basic positions seem OK, so these things are not too serious. Characterize your pedagogical work at improvement as "refinement" rather than "correction" or "change," concepts which for beginners often lead to more "change" than you actually want!