need help!!!!!

Chicken came from a growing house, ones that got away. There age now range from 3 to 4 month. Several have died, new & older ones both. It seem like one a day now.
Lack of energy & appetite,
Nasal discharge,
Eyes Watering,
Coughing,
Gasping for air before dying
Seem like I have tryed everything,,,,, Sulfamethazine,drinking water solution, sulfadimethoxine drinking water solution, all liquid form.Sulfadimethoxine powered form which
you mix it with water...Soon of the chickens seem to be dealing with it. But still showing sign of it ,coughing, watering eyes, nasal discharge,, but have good appetite and maybe
gaining a little weight.....but I'm thinking it get them to. Several people are telling me that these chickens will not live in the out side world... Is anybody out there got a solution
too help me prove these people wrong,,, and save my chickens!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

 

thanks for the reply, it was helpful,,, but I'm kind of lost right now,,,, chickens dying one too two a day,, information overload right now,,I guess reading to much,,,read
somewhere tylan,,,, give it under the skin... read somewhere put it in the brest,, somewhere it said to put behind the neck,,,,, decided to quite inj.... started to feed can corn
with yogurt and blended up blue berries,,, got a acrea so I dont have to pay for them, went back to using vetex,,, and also using polyvisol baby vitamins, but looks likes
more chickens are getting weak,,,,:

 

thanks for the information!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!I need it!!!!! Another ? if anybody knows please reply.. Feeding them yogurt to build stomach culture back up,,,
someone told me that buttermilk would do just as good, any thought on buttermilk