There is some info on Oxine AH on the "Fungal Conditions" on my website linked in my sig below, if it might be of help.
I've used Oxine as a nebulizer for chickens that had MG. It did not clear up their particular strains of the disease. It may have helped reduce the severity, and I definitely think it helped keep the coop disinfected so they didn't pick up fresh doses of germs from poop & air as much.
Oxine only can work on germs inside a chicken if it comes into physical contact with them. I'm thinking that's mostly only when breathed into the chicken's lungs & air sacs, or passing through the chicken's digestive system. My thought is that Oxine would not be very concentrated in the bloodstream & wouldn't reach other organs.
I don't know all the areas of a chicken's body affected by various diseases, but if a disease is being harbored in an area Oxine can't reach, you might have to also use additional treatment(s).
My recommendation for a fairly developed respiratory condition would be to use Oxine (which really does appear to be GREAT for many situations) and ALSO give the chickens antibiotics (such as Terramycin) and/or probiotics (buttermilk, unsweetened yogurt, etc) and other health supplements.
There is a
Poultry Medicine Chart on my website, too, that can give a start on choosing which medicine may be helpful for a particular health problem.