We’ve had 5 hens and a rooster for 1 year. I thought the hens were molting, but now I'm not sure. The feathers are gone from around each hens' vent, and the feathers on their backs toward their tails do not look good. I've checked for mites and lice and found none. I try to let them free range for 1 hr a day. The chicken run has sand & a large part of the sand became hard due to rain, & I've tried loosening it with a hoe. Could the hard sand cause the feathers to be pulled out of their bottoms?