some of my hens continue to lay on ground inside the run rather than in the nesting boxes. I have 9 boxes in the chicken house and about 15 hens, only 2 of the 9 boxes are being used. I placed a 3 hole box on the ground thinking maybe that would be easier for them. After filling these with straw, the hens only raked all the straw out and continue to lay on ground. any suggestions?