Take the pullets out of the nests and put them on the roosts after dark....The coop already has 2 roosts the old girls occupy the top one and the lower one is empty.
....or....
block off the nests at dusk, then unblock them well after dark, this will force the pullets to go to the roost.
Either way might take a week or more of management until they all get settled into the new habits.