If the area is secure you could just leave them to it Shygirl. Sure they will use the coop when the weather gets bad. Worth checking the coop for red mite as that may be discouraging them. If the area isn't secure can you decoy them, with treats before dark, into a run attached to the coop and then lock them in it so they have to use the coop?
We acquired a Leghorn bantam cock because the hens used to roost in the trees. One by one the fox took the first one down until only the cock remained.