Last night, I changed from shavings to sand in my coop. Today, when I got up and went to check on them, they weren't walking on the coop floor! 2 we're on the roost, and they other in the nesting box. They will go get their food/water, but soon after that they go back to their places! Why do they do this? I had to bribe them with mealworms to get them to walk to the middle of the coop. Then they went back. Please help!