What wattage light are you using?. It looks awfully bright. But you say, this condition happened before and not in this cage? Be mindful that the skin of the chameleon does not have to touch any part of the screen or the light to get burned. They get what is called a thermal burn. Kinda like us getting a sunburn. I have seen many, many chameleons on here with their spines burned off. They will never grown back once they are damaged or fall off by the way. It could be too that he is burned and now the burn is infected. I have never heard of the superworm or meal worm beetles biting a chameleon. I have heard of crickets left in the cage doing damage to chameleons, however. Not saying that it could not happen with the beetles, just don't recall seeing any case of it, atleast not on this forum anyways.