potential problems:
Unexpected matings too young, female goes eggbound.
Canabalism.
Stress causing one or both snakes to stop eating.
I'm dealing with that last one currently, actually. My snow and my anergy did fine being housed together in a 55galon fishtank habitat for several months. However, though both were initially eating quite well, the anery quickly grew much larger than the snow (she is now at least twice the weight of the other, if not more so). I began to notice the snow cruising the tank more frequently. She began to refuse meals, then stopped eating entirely. After 3 or 4 weeks of this, I put her in her own 10 gal tank. Because she is a very nervous snake, she only eats IN her tank, so I'm placing thawed 1-day old pinkies in her hide every few days. She is eating the majority of them at this point, and should hopefully begin gaining weight soon. In fact, I just tried her on a larger pinky and having literally just now looked in her cage, I can see a nice big bulge. She's no longer cruising her cage during the day, and is calmer when handled too, even though she's still a very nervous individual.