All hens suddenly stopped laying, and other issues

Reaching the end of all ideas...help?

We have a flock of 20 chickens - 17 hens and 3 roosters. Two of the hens are 3 years old, one rooster. And a handful of hens are a year, and the rest will be two years in December. We also have 17 littles who hatched in August, who will be replacements for the aging hens. We were getting about a dozen eggs every day until the end of August, when they abruptly stopped laying. Like, 12 eggs one day, and nothing at all since then. The day before they stopped we had a hawk take a chicken, so nothing the next couple of days we chalked up to trauma and being frightened. But nothing, not one egg since then. Something HAS to be going on, that our very regular layers suddenly stopped. We noticed in hindsight that our roosters stopped breeding the hens around the same time. It was a rooster on a hen every five minutes here, and there has been zero activity for weeks now.

They have free run of an acre. They get layer feed with oyster shell mixed in daily. We have four water tubs around the yard that are rinsed and filled daily (they share with our Pygmy goats as well). I dewormed them right after they stopped laying. I throw scratch grains around a time or two a day, but they appear to be healthy weights. They have a secure coop that is cleaned regularly. There have been a few In various stages of molt, but not enough that would explain no eggs for two months. Our days are getting shorter but but not enough to change laying habits that much IMO...we're in Tennessee, and it's not getting cold yet either.

Any ideas on what might be going on here? We're at the point that if we can't figure it out soon we're going to cull them all and wait for the two month olds to start laying in the spring instead of feeding them all winter for nothing. I can't come up with anything else......

 

We've looked everywhere for hidden nests, nothing. Last year we didn't start giving light until November and they didn't stop laying - they slowed down but didn't stop. The combo of no eggs and no chicken lovin' have me thinking something is wrong...our Roos have always been horny buggers, so for them to just stop is strange.