It could depend on several factors. Did you brumate your snake, either on purpose or by accident (decreased temps without really knowing it, perhaps due to an extra old spell, reducing ambient air temps that heaters couldn't compensate for)? Any slight increase in normal temps and/or lighting which might cause the snake to think Spring has already come? I've purposely caused my corns to initiate breeding by adjusting their surroundings (earlier cooling and then earlier warming), so it could happen.