worried about little duckling

[korme5]

Hello again guys ! So I have had my two little ducklings for about 3 weeks now and I got them both as day olds and now the one I know to be a WH is huge! And the other one who's breed I don't know still looks like he is a week old!! The big one is losing his baby feathers and getting the awkward feathers and the big weird bill! while the little one is still all downie. He is getting heaps of food and he has a layer of fat, no bones or anything, and is more active then the big one. So should I be worried or could he just be a late bloomer? Or could he be a smaller breed?? He is yellow but has golden stripes near his eyes and on his back so I dunno if that helps with breed?? Here are some pictures so you can see, they are just out of the bath\shower so are wet but you can really see the size difference.
Any help would be awesome!!!

Big one is Hades little one is Hermie (yes like the Greek gods )

 

[Amiga]

You could have a different breed, or you could have one of those ducks who has a hard time developing.

I would give them both some poultry vitamins once a week or two, keep a close watch, maybe give Hermie one extra drink of vitamins during the week. Some ducklings have higher B vitamin needs.

Some have congenital challenges - and don't grow to full size, or take much longer.