Thankyou for the replies.
My RSL & Delawares are currentyl 14 weeks, the Barred Rock 8 weeks. I am still working on "integration".
Currently the older girls are in a large (60' X 60') run from early morning (repurposed dog yard), in the early evening they are returned to their coop/smaller run. The younger two go in there during the day (with a covered area they can retreat to), but have a separate shelter for night.
I wanted to get an idea on the earliest they may start laying, so I can start to leave the older girls in their coop/run till late morning. Also, I still have the nest boxes closed off (they were sleeping in there, but now appear to be roosting). I think I'll uncover the nest boxes now, and in two weeks or so keep them in the coop/run area longer in the morning. (The larger run is not attached to their coop/run - unfortunately.