If the chick already has cocci, then (from what I understand, so I may be wrong) giving the medicated feed won't help at this point. You will have to give some sort of medication to the chick (by hand if he/she isn't eating/drinking) in order to treat the cocci.
Chances are your adult birds...
They look exactly how my chicks have looked with cocci. It is a protozoan that is common in soils and until they develop a resistance to it, chicks are susceptible of getting a cocci inflammation in their digestive tract. It is not contagious like a col in humans is, but rather something that...