Hi, thanks for joining us. You've been given some good possible causes...health, breed, nutrition, hidden nest, over breeding, etc. If you check out each of those possibilities, you may well find your answer. Good luck!
I do not find it uncommon for my silkie roosters to get along. I have two roosters and two hens in one breeding pen as we speak. These do not overbreed the hens, but as mentioned above, if they are, that would stress out the hens, and they may not lay.