Your values are rough. If you set all of your paintings to grey scale, none of them read very well.
Idk if you're trying to improve or not but here are some reliable resources for rendering/lighting/form.
https://www.amazon.com/Dynamic-Light-Shade-Burne-Hogarth/dp/0823015815
https://www.schoolism.com/lp/fundamentals-of-lighting-sam-nielson/