Month old runner duck is sick HELP

[sillygoose]

My month old runner duck seems to be losing weight, he feels bony and is very inactive. When I pick him up, he dust sits back down when I put him on the ground ( normally runs away) he is still eating an drinking but doesn't want to swim like he normally does. He has a white, dry crustiness around both eyes. He is with other ducks, and the rest are all behaving normally. He has only been acting this way for 2 days. His droppings are white and brown, of normal consistency. His feathers are just coming in, and my mom said he may be "feeling unwell" due to the feathers and that the crustiness could be due to eyelashes coming in. Is this a possibility or should I deworm him and maybe start him on antibiotics? There is no vet in my town otherwise I would take him to one. Please help! Any advice is appreciated! He is kept in clean conditions with fresh water and "duck grower/ chicken scratch " feed. Please help ASAP!