I sold some of my polish chicks to a gal and she called this morning, one of the has chicks died. It had white crust on it's beak and head. Now some of the others are showing some crusting on their beaks. I told her to change the bedding and wash down the brooder to disinfect. I checked all of my remaining chicks and show no sign of the crusting. Has anyone heard of this? What is it? What can we do to prevent it from happening again? Thanks!