I hatched 2 Rouen ducklings yesterday. I put them in the brooder this am but they are very weak and lethargic. They won't stand up....they're just laying there.........they do chirp alot. I picked them up and tried to get them to stand but they just laid back down. What could be wrong? This is the 1st time I've hatched ducks, but my silkies were up and running by this time.