these duckings are literally two days apart! the bigger one is Tomoe and the smaller is Levi. Levi and his other brothers/sisters are all the same size and even hatched on different days (including the one who hatched with Tomoe.) Tomoe is a week old today and is very big! at least from what I've seen with other ducklings I've hatched, they don't usually get this big until 2 and a half weeks.
Some ducklings do seem to break the growth speed records. I would be sure to give some poultry vitamins once a week. They are so cute!!!