I'm really surprised they didn't treat with clindamycin. It targets mouth issues and works faster/better than baytril. It seems to me that little guy needs a very good mouth inspection and different meds. It looks like its one of three things to me without a culture being done.. Mouth rot, a severe RI, or an I jury/irritation caused by either a broken/abscessed tooth, or bedding. If its a tooth issue it would require treatment by something that targets mouth infections. Possibly on and off until the damaged tooth comes out, or swelling is down enough to pinpoint it for removal.
You really need to see a better herp specialist and get a mouth culture done to find out what type of bacteria is in there, and one who will take the time to explore these other obvious possibilities.