Yolks flat and breaking
Age, pure and simple. I used to be a free range egg producer and our chickens were retired to homes happy to have them as pets and occasional layers by the time they were two years of age.

Eggs become larger as they age but as they get beyond two, most hens lay a lot less and quite frequently the eggs can show their age on the inside as well as outside.

Like humans, hens have only so many eggs they are born with and once those have all been released everything starts to slow right down until it stops completely.