Just checking a Beardie book "The Bearded Dragon Manual" by Philippe de Vosjoli (and others).

In the trouble shooting health chart section it mentions; Infectious Stomatitis, "Mouth Rot".

"Unusual in bearded dragons and usually secondary to weakened oral tissues as seen with low calcium. Increase heat; offer a good basking gradient. Gently clean oral tissue with dilute Betadine, removing all the loose and dead tissue. For all but the mildest cases, see veterinarian for antibiotics and to correct underlying condintions"

Hope this was helpful.