I’d put my guess on batch of hens not as good of layers.
Is your source of chicks the same? From some origin? Bc would guess different flock genetics from your stellar layer to this batch.
We had some dark brown Leghorns that took forever to lay. Finally sold them as they were sporadic layers too, producing only medium sized eggs. When I called the hatchery to order some more chicks of different breeds (small hatchery, happened to speak to owner), told them about these DBL and their paltry egg-laying. The owner ssid that they were not their best egg-layers (they are listed as exhibition quality), and that they were not surprised by the lower egg production. So, in this case genetics played the key role.
FWIW, the Plymouth Barred Rocks we have are consistent layers of nice sized, evenly colored eggs. Good personalities too, my tween can get them (and only the PBR), to jump up like a dog to get a treat that she holds high for them... so, we purchased 2 more from same source hoping for similar experience.
I hope you are able to get some good layers. If you want great egg layers you can go to production stock, but often need to turn them over frequently (often by around 2years old) to keep up production numbers. You can search for other breeders that may be breeding for overall egg laying longevity if you want PBR.
