He is very handsome! Are you sure he is only 4 months old? He seems big for his age, but I have never had a veiled so I have no clue how fast they grow. As for the back leg I remember hearing something about gout and it resembles that a bit. If I remember correctly gout is from a high protein diet. Some here have linked gout to gut loading crickets with fish food. I am not very informed on the subject so I found you a link to take a look and I am sure one of the pros will comment soon! (I tried to find some pics of gout in chams but couldn't find any sorry

)
http://www.mythicalchameleons.com/vetcases.htm#gout