My Chicks and ducklings I just recently got have developed a skin rash?

About a week ago I got chicks and ducks and they all live together in a brooding box in my bathroom. I switched out their bedding to pine shavings and then two days later noticed they had developed red, irritated skin and ruffled exposed feathers around the irritated spots. I first noticed it with the ducks and the chickens slightly later on. Any possible advice on causes or solutions?