Mouth Rot?

One of my hatchlings has some problem around his mouth. Just below his lower beak there is an off-white lesion of some sort, and on the right side of his face there is a light orange discoloration. Worse, there is some kind of defect in his lower beak. When his mouth is shut, it looks like there is a hole between his lower beak and neck. It looks like if I probed it, I would enter his mouth. (I’d noticed something like this when I got him but thought it was a natural defect.) The hatchling is very active and has a strong appetite. My other hatchling and my juvenile Reeves hav none of these symptoms. I could use some help re identifying the problem and proposed treatments. I have a bottle of Nolvasan. Should I topically treat or dilute and soak him in it? Please help.