Have you been feeding both of them often enough? A good sign of of follicle development is aggressive eating if I recall correctly. I think one of my 1000gram females is actually developing follicles even though she is underweight because of the temperature drop and the aggressive eating. Plus I've palpated her and felt what I believe are follicles. Breeding can induce follicular growth but what I've been told, feeding is a huge indicator.

This is just going off my own research and my limited experience with my own snakes.