We have a mystery breed chick (bantam) which is 6 days old. It is super happy, eating, drinking, and running around. Totally normal chick except it has the nastiest, smelliest poop ever! Its kinda runny medium brown, and smells like hell. Is this normal? We have 4 other chicks that have totally normal poo. So I am confused. Also, they are all vaccinated for Marek's and are on medicated feed. Help?