I have 9 mature hens. They range in age from 1-6 years old. While I was on vacation for 3 weeks, my husband said we were getting 5 eggs a day. He ke[t them in their 1/4-acre enclosure. When I came home from vacation, I started letting them out to free-range again, and we dropped to 1 egg a day - overnight. I figured that they probably were hiding eggs out there somewhere, so after a few days of this I started keeping them in the enclosure all day to see what would happen. We've been getting 0 or 1 egg a day now for 3 weeks, whit them in the enclosure. No hidden nests. No egg-eating. The weather doesn't seem to have changed much. We've been in the low 80's and sunny pretty much all summer. No changes in diet. No mites, lice or worms. My ancient, giant blue Cochin is molting, so that explains her, but she only lays a dozen eggs a year anyway, so I don't really count her.