There are quite a few on the forum who have treated yellow fungus with Voriconazole.
Are you giving probiotics as well? How long has your dragon been on the medication?
Is he eating very well right now?
I hope he is faring well on the treatment.
This is a rare fungus that attacks an immune compromised host. Possible he could have lymphoma or adrenal insufficiency. Back to vet next Saturday. Maybe lab work.
OH I hope it isn't a cancer. A blood test would definitely be helpful to test his kidneys. Does he get adequate hydration regularly?
Let us know how the vet visit & blood test goes.
Is he eating much right now or maintaining his weight or losing weight?
I am spoon feeding veggies and Grub pie daily with Vits and Calcium. He gets soaked outside in the sunshine daily. He gets up every morning and gets in his basking spot. He poops 2-3 times a week. All sounds good but he will not eat on his own and he closes his eyes a lot. Don't think he has lost weight. Mouth is nice and pink.
It sounds like he is doing well though, overall. At least you are managing to get food into him then pretty easily.
The outdoor time should help quite a bit. Does he seem to enjoy it also?
I am glad to hear he gets himself up & he basks normally. You could try getting some bee pollen to help out with his appetite some as well as immune system, too.