Some have been vaccinated and some were hatched here at home.
They get weak have trouble with balance and die within 3 days.
I have wormed them and treated for cosicosis (sp)
I have had this happen 5 times in 2 years. I raise the chicken all different hardy breeds until about 7-8 months old then they get sick and die.
They free range in a fenced area, are my pets, have clean everything.
Some I have had the whole time and are fine?