i have had fertile eggs from him before so he's definitely not sterile, i also hadn't seen him breeding then hens for a while, yesterday though he was all over the hen so he's obviously feeling his oats and the need to dominate now. I really do think he's just slacking3 days after mating eggs should be fertile - if you are still depending upon only your original rooster there is the possibility that he is sterile rather than 'slacking'.