No foul odor leads me to believe that you're possibly dealing with Infectious Bronchitis (IB) or Mycoplasma Gallisepticum (MG.)
Again, please refer to the link in post #5 and read up on both these highly contageous diseases. Remember to practice biosecurity since you're not going to cull and...
Since you suspect Infectious Coryza, here's a link. Scroll down and read about it, as well as treatments. Do not mix anything, including ACV into sulfa based meds. BTW; you didnt mention if there were a foul odor enaminating from the head area of your sick birds. If not, most likely it's not...