I wonder if you have MG in your flock. I brought home a bad strain from a swap last year and found that it affects laying and hatching. Before you all think I am an idiot
I quarantined for a couple of months and the carrier birds appeared perfectly healthy. As more of my young flock got ill with sneezing and respiratory problems I heard from others that they were having the same problems from the same seller and we came to a consensus that it was MG.
I treated with Denagard and it solved the problem. Even treated the main flock in case I had carried it to them on my clothing. This is a disease that can be spread by wild birds as well and I think that it was lurking in the laying flock. After treatment they started eating more and laying almost doubled. It is a disease where the chickens (and turkeys) can have it and show no symptoms until they are stressed, and then it crops out. One of the symptoms that you might not notice is reduction in laying and mortality of embryos and chicks.
The Denagard has no withdrawal time and it is safe to eat the birds or their eggs. The original carriers are clear now and any bird that still showed symptoms was culled, as these would be carriers. Denagard is said to eradicate the organism in many instances and there is no resistance built up. It is a liquid swine medication that is diluted in water and given for 5 days initially, then 2 days monthly until you are sure it is gone.
I'm not giving medical advice here, just recounting my experience. It devastated my turkeys and they were sick enough to die when I started treating them. They all survived except one that I lost a couple of weeks ago after it fought through the winter. I set eggs and half were fertile, which isn't bad because it was the first eggs laid by the hens and I am not sure the toms had the hang of things yet. In an MG infected flock the eggs often do not develop at all, quit in the middle, or the chicks die within a few weeks.
Just a thought, Lynzi, if yuo are not getting a lot of eggs and your hatch rate is poor.