Almost all of my chickens are sick with this to one degree or another. They are congested, sneezing, head shaking, matted eyes, watery eyes, crusty beaks and open mouth breathing. This started last week and i have lost 7 of them so far. I started with duramycin 10 in the water last monday and that didn't seem to help much since several of them were too sick to eat and drink. I stopped that and started tylan 50 (I am confused about the dosage recomendation some say 1/2cc some say1cc) and bactrim 1/2 tab for standards and 1/4 tab for bantams. Some show improvement and some not so much. When should I expect to see improvement after starting this drug? Some of the chickens don't show any signs at all, should I be treating them too?