Could be a possible URI, or, upper respiratory infection. My sully had one because we went away for a week and her bulb burned out. My vet suggested that I raise the basking to about 105-110 ish. He also gave me some nose drops and gave her some shots in her legs.
You could try raising her temp and lowering the humidity. If it doesn't clear up I would definitely take her to the vet. good luck.