I would take him to a herp vet. He looks very malnourished to be 2 yrs old!? Those lesions could be a sign of a nutritional disease. To only be fed once a month borders on cruelty. Underweight and malnourished is a recipe for disaster. He could be septic with a blood disease as well. He definitely needs a vet work up. At least to rule out a couple of things. Good luck.