Why have my 7 month old hens not began to lay?

[Clarity1210]

My 3 Barred Rock pullets born the first of June started laying around Thanksgiving. I've consistently gotten a dozen eggs every 5 days since then.

My Easter Eggers born the first week of June started laying the day after Thanksgiving, my Barred Rock and one Blue Cochin the next week, all in the nest box. One of the other Blue Cochins must have started about New Years, as last night I found a clutch of eggs in the bedding near the nest boxes. This leaves 2 June pullets to lay yet (unless they also have found an alternate site). Only one Easter Egger and the Cochins showed any interest in nesting before the first egg. Give them time!