My free range flock is showing signs of cocci and i began treatment today with corrid. These are two and three year hens. my three year olds had cocci before but one is obviously ill. My new flock is twelve week old and penned near the others. They were on medicated starter until eight weeks. Should i treat them as well. They seem ok but i want to be safe. I have had a very humid damp spring summer so far in maryland. Would you treat the rwelve week old?