Can you post a picture of their whole housing?
Do they stay on that ledge all the time?
I would put the feed in a feeder or a container that is secured somehow, there will be lest waste that way and it will stay cleaner.
Sometimes a chicken will eat feathers that they find, I would make sure they have a source of grit (crushed granite) since they do not go outside.
Extra protein is always a good idea for molters - egg, tuna, meat and I usually give poultry vitamins once a week too.
Re-treat them for lice/mites at 7 day intervals with a Permethrin based poultry spray or dust.