So our chickens have decide the spot that used to be our burn pile for yard debris is a perfect dust bath. We burned everything in the pile this spring and now the barren ashy spot is enclosed in their chicken yard. Wondering if it's okay to add the ash from our Weber charcoal grill to the spot to renew the dust in the spot? Since we use lighter fluid to light the briquettes, didn't know if that would leave a residue in the ash that would be harmful to the chickens? Anybody know?