What is the quality and amount of discharge you see? What symptoms were occurring prior to starting medication (i.e., was there sneezing) and what is still there (i.e., is there still sneezing?).

In short, if there were typical URI symptoms prior to Baytril, like colored discharge, excessive sneezing, etc.,  and now there is no sneezing and the discharge is very minimal and only clear, I would not be too concerned about it cropping up on occasion. As a rabbit owner who is monitoring for URI symptoms, you will be very sensitive and alert to when the nose is wet; in reality, sometimes the nose looks a little more wet naturally due to hay dust and other irritants in non-URI rabbits sometimes, so what you see could be normative, depending on amount and color.

She could need a different antibiotic. Do you think you could do a culture to see if another antibiotic would be better? And sometimes they do take a very long course to fully clear the infection.

Sometimes they will just try a different antibiotic without doing a culture. It would definitely be more cost-effective, even if you get to antibiotic #3. Azithromycin is often tried for “stubbon” URIs.

IF a different antibiotic doesn’t work, then I agree with the vet that you may want to consider doing X-rays. Considering her age, she could have something else going on. Tooth roots growing into the sinus cavity, for example, can cause chronic sinus irritation and infections.