We are in a bit of a downhill slid. A couple years ago I introduced Marans to my flock. I paid premium prices but these are not premium birds. I have had nothing bug genetic issues in my hatches and birds with a weak immune system. Egg bound and sour crops too. Only ever with the marans. All my other birds are fine. Problem is as older birds passed I have kept up my numbers with marans. Great layers but gah always something wrong. Every hatch I will lose about half of those egg that hatch. Crossed beaks and deformaties.
So My maran roo is meeting mr axe and the girls will slowly be phased out. I plan for now to focus on the full blooded ones and let the mix breeds be. It seems with the mixing I still get a fair bird. I think. Should I consider weeding these out too? I think I need to start over a bit. Opinions on better breeds. I do have a breeding trio of lavender orps that I was considering putting in the breeding coop.
Sometimes just introducing new blood will end those problems. Your flock may have been too inbred. Get a new rooster, maybe even two, from different sources and maintain two different lines that you can cross later down the line when genetics get too close.