Do they have places to hide? You might stop with the seeds, since those are a treat. Treats shouldn't be more than 10% of their diet.
Overbred is not the same as over producing. If your male is too aggressive with them, that can cause stress. Anything that causes stress will stop them...
What is their setup like? Are there any predators hanging around? How invasive is it when you clean their pen?
You might try upping the ration of hens to 5:1 in case they're being over bred.