We collected 4 khaki campbell ducklings last week from a breeder which makes them 5 weeks old. One of them was a little larger(named her Nessie) than the others and remained on her own. The other three are smaller and play more together. The others cuddle up and put there beaks onto Nessie at night. During the day the others are standing and playing while Nessie remains more on her own, she drinks, eats but lies down more and seems to pant more when she lying down. We've been letting them play in the bath in the evenings for about 10 minutes but have stopped that for fear she has got a chill. The other difference is that when we pick them up in and out of the bath the others are skittish and don't like being held while Nessie just settles into our hand, and when we put food down they all rush into a corner scared while Nessie just stands there seemingly unafraid. I don't think this is normal behaviour for a 5 week old duckling. Has anyone got any ideas what is wrong, we obviously don't want to lose her, she's watching us all the time and seems to be very clever. We're feeding them starters crumb combined with growers pellets with chick grit. Has anyone else experienced this?