Okay, Y'all, time for Unsolved Mysteries
Out of 6 pullets, all from the same hatch on 7/2/16, one & possibly two are laying, and have been for a month; the others never have. The only possible difference is that they're not all necessarily from the same hen. At first I thought they may be laying in secret nests when they're out & about, but they've all been confined to the coop/run/chicken yard since a hawk nailed one a week or so ago. Even before that, I kept them up for a day on two different occasions with no results.
I'm out of ideas.