My chickens seem to be spending a lot of time mid-morning and mid-afternoon loafing upstairs ..... do you think a low roost in the run below would cut down on that?
A roost might help. My birds often have periods during the day where they choose to roost and preen themselves--just sort of hang out and chill in the run.
My girls also seek out shady spots at certain times. Might your birds be inside to get out of the sun? The time of day you describe could be when the sun might be coming in at an angle and so hitting them directly.