Less calcium in the feed?
It helps quite a bit to smash up the shells one uses themselves, and feed that back to the hens. Just get ‘em smashed up into SMALL pieces — we have a couple hens that lay unusually thicker shells than the others and chunks too big (such as if certain birds start consuming their own eggs) along with tougher grasses and such can clog them up.
I’ve seen no drop off not attributable to weather, but, we use Rural King feed, not Tractor Supply, and, our chickens get to free range some days.
“Less calcium in the feed?”
That is a good guess see #48. Possible Lycine deficiency.
You beat me to it. See above.