Unfortunately, your order of ducklings is having it rough. They hatched Sunday/Monday, shipped out Monday night and then hit shipping delays in getting to you. Then factor in the cold. They had a very rough trip and unfortunately, you are seeing the result of that.
If you don't care what the replacements are and are willing to risk the weather for shipping delays again, you can have them resend some ducklings next week if they have enough after they fill their other orders. Or you can wait and have ducklings of a different age which can be kind of a pain. Chick days have started here in Central NY already, so I'm guessing feed stores and the likes are getting theirs in now too if you want to go that route.
Good luck and hopefully you've seen the last of the rough ride.