It is most likely that the days are getting shorter. I have a large flock and they are also moltng, so they are only laying about 10% of their summer production, now. I have plenty roos and they don't seem to lay any better with fewer or more roos. It's just that time of the year. We had such a mild winter, the hens didn't stop laying since last summer, so it was time for them to molt, I think.