Going to get some new chicks today but just found out they were not vaccinated for mareks. My older three chickens all came from hobby breeders who I doubt vaccinated. Would it be best to buy the vaccine and vaccinate the new chickens myself or just leave them be. I have corrid on hand in case cocci rears its ugly head. Anything else I should be prepared for? The chicks will be isolated with proper measures for at least 4-6 weeks