So I've read that hens can be fertile 3-4 weeks after being with a rooster. What is the longest a hen of yours has been fertile with the absence of a rooster? Can eggs a day or so after 4 weeks be fertile?
4 weeks would be really pushing the envelope but I suppose it's possible. 2 weeks has high confidence and 3 weeks would be spotty- some hens would have fertile eggs and others not. You can always crack one open and see if it's fertile. Or start incubating and see if they start to develop. https://www.backyardchickens.com/t/16008/how-to-tell-a-fertile-vs-infertile-egg-pictures
