I have 3 chickens and 4 nesting boxes in their coop. All 3 of them lay in the same box. Yesterday, 2 of my girls were fighting over the box. My barred rock muscled her way in there after my EE had been in there for awhile. I have 3 other boxes that never get used. How can I get them to use the empty/unoccupied nesting boxes? They are driving me CRAZY!!