from the picture he looks pretty darn good. The 6 lbs could be the switch in food and all the exercise he's getting, his metabolism is really high from the sounds of things so that could explain the weight loss as well. I would suggest increasing his food by about 1/2 cup - 1 cup a day and see if that does anything. From that picture though, he's in excellent condition. His body may just be burning off the weight as it sounds like he's solid muscle without an ounce of fat on him lol.