hey! i had a really similar thing with my BO chick! it came on suddenly, she had mucus grossness and was very lethargic. separate the chick from the others, give it water through an eyedropper, pray pray pray and pray more(!!!!) and sing to the poor lil thing. mine pulled through, maybe yours will too! it took about 4 or 5 days though..just dont give up hope. message me if youd like, maybe they had the same thing! i still have no idea what was wrong with her..