I would always recommend a culture be done with RI, ALWAYS. It will allow targeted antibiotics, a vet using Batryl as a kill anything hammer is not helping. Batryl is heavily used and the growing amounts of resistance to it attests to this. It also points to the need of a culture. Most say that to do anything an antibiotic need to be administered for weeks and weeks with reptiles (24-48 hours to digest compared to 20 min for humans everything is slow), the last rescue I had that was treated, was treated every 3 days for 4 weeks. Then a new culture done to confirm it was clear. Two treatments of antibiotics is unlikely to have any effect and it is unlikely nebulizing also would have any effect. It is quite likely there was no RI and it was mis diagnosed by the vet. It is quite common. RI does not go away in a week or two. Humans with pneumonia blowing liquid from their lungs get hospitalized often for weeks. A snake who has a system moving 60 times slower is not going to recover to 100% in a week or two under any circumstances.
We ask a lot of vets. The be an expert in cats, dogs, all manor of small mammals, large mammals, a huge array of reptiles and birds. Each one being different and having its own ins and outs. A human doctor is so specialized that there are left side heart specialists and right side. How can any vet know everything about every animal? They can't the mark of a great vet is one who sees something new scratches their head and then picks up the phone to talk to an expert in that animal. This is not what many vets do they try cross over treatments, this would on ferrets so it should work on...