I've had a couple of different roosters and have had high fertility rates. My current rooster's fertility was good last year. He's just turned two and most of my hatches this year are crap - lots of unfertilized eggs and hatch rates of 50-70%. He's in with 20-25 hens which is high but that's never been an issue before. What have you experienced about declining fertility in your roosters? Age? Or other factors?