I have a 3 week old black sex link chick. He was the only boy of the bunch I got from the local Co op and he started out very healthy and aggressive. He was very spunky and food oriented, but lately we've noticed that the other chicks are MUCH more developed than he is, even the smallest of the others is sporting tail feathers and a fuller set of wings than this boy. And recently I noticed that he has lost interest in food and doesn't want to eat or drink. He's beginning to become lethargic. I've started giving him sugar water with a dropper tonight, and he's still got enough fight in him to resist pretty good. He also peeps and flaps around just fine when I handle him. He just isn't himself and is acting rather sick, my biggest concern though is the huge size difference between him and the others. What could this be? And what can I do for him?