Just about 100% certain this is a thermal burn. Classic location for one. The actual temperature directly under the basking light at the perch she sits on is too high. You will need to adjust your temps either by lowering the basking perches or raising the lamp higher off the top of the cage...
You may not be seeing him drink if his cage is full of foliage and lots of droplets available much of the time. That's how it should be. What is the range in humidity in his cage during the day/night? If it is correct he may not be drinking because he's hydrated enough. Some chams drink in...
Well, this is the justification for keeping BOTH species. The cham is the main herp desired...the beardie is the antidote to the cham. Substituting a dog for the beardie works too.