I was in a similar situation with my first ducks being Pekins. I wish more instruction would come with them! They are unfortunately bred to put on weight super fast as they are meat ducks, and their poor little bodies often can not keep up 
. The liquid vitamin B complex is like a rescue med once a problem develops, it's stronger than just adding regular niacin, so that is what you need at this point. If the foot itself is at all curled, you need to make sure it starts developing flat, and you can do that by cutting out a tiny piece of plastic in the shape of the foot and using vet wrap to carefully attach it to the foot without cutting into it or anything like that. Make sure you support him as much as possible - give swim time a couple times a day to exercise his legs, support his body as he preens afterwards, and keep his food and water close so he doesn't have to walk too much - likewise, you don't want him to overdo it keeping up with the other ducklings. It's best to have the surface of the brooder something that's not slippery. If after reading through some of the threads on BYC you feel he may have a slipped tendon, you'll have to take other measures. Sorry, I can't advise you in that department as I have no experience. I wish the best for you and your little duck.
. The liquid vitamin B complex is like a rescue med once a problem develops, it's stronger than just adding regular niacin, so that is what you need at this point. If the foot itself is at all curled, you need to make sure it starts developing flat, and you can do that by cutting out a tiny piece of plastic in the shape of the foot and using vet wrap to carefully attach it to the foot without cutting into it or anything like that. Make sure you support him as much as possible - give swim time a couple times a day to exercise his legs, support his body as he preens afterwards, and keep his food and water close so he doesn't have to walk too much - likewise, you don't want him to overdo it keeping up with the other ducklings. It's best to have the surface of the brooder something that's not slippery. If after reading through some of the threads on BYC you feel he may have a slipped tendon, you'll have to take other measures. Sorry, I can't advise you in that department as I have no experience. I wish the best for you and your little duck.
Hopefully the suggested Niacin supplementation will help.
. But I have a couple ideas to try and save this little guy. I’m very stressed about this. I’m going to completely seperate him and give him more niacin, I ordered brewers yeast and I made splints for its legs and want to make it like a hammock and cut holes in it for it’s legs so at night when it’s sleeping it can relax without putting weight on it’s legs. And of course, water therapy. I just wanna help him. Please tell me if this is a good idea or if I should put him down? I don’t want to do that. But if it’s for his own good I will.
