I have a duckling who was severely pigeon toed, Which I figured was from a niacin deficiency after about a week and a half of adding more niacin to his diet I noticed improvement. He’s nearly 5 weeks old but he’s half the size of the other ducks , he’s been smaller then the other ducklings ever since he hatched. I had put him with another younger duck but even he’s starting to grow bigger than him. Any ideas to help his growth?