Do you see any bubbles or foam in an eye? Is there any rattly or congested breathing? Can you clean the nostrils with a few drops of saline or hydrogen peroxide, Qtips, or if totally blocked, use a wooden toothpick to get the nostril open?
It sounds like she may have a respiratory disease, such as infectious bronchitis virus or MG. Viruses do not respond to antibiotics, but if she has been lethargic or not drinking well, she may not be getting enough of the antibiotic to treat MG. There are other viruses and bacterial diseases. How is your coop ventilation?