My male Pekin duck, about 6-7 weeks old started limping the day before yesterday. I have no idea what happened to him. In the mornings I herd the flock from the barn to the pond to graze and they put themselves up at night. I noticed the limp when he was having a hard time keeping up (I help out if he gets left behind. He is able to get around under his own power (slowly). When he swims he only uses his right leg. Should I just let him be as long as he can get around? I don't know if he's in pain. When I palpate his leg I can't feel any remarkable deformities nor does he react as if it's hurting him. Is it humane to just leave him alone? Here's a video of him.