I have a large coop with a dirt floor( ground that used to have grass) . Its covered with tin and has 2 clear panels to allow for sunlight. The front of the coop is open with a 1/2 in mesh material. We added a drainage system but it is still damp on the floor. It now has green patches of mold growing on the dirt. The chickens only sleep in the coop. During the day they free range. What can I do for this?