Hello, I have 7 Pekin/Runner mixes that are approaching 3 weeks old. As I have started letting them run around and swim more, I have noticed that one of the smaller ones is always lagging behind the others. She paddles around slowly in the tub and needs to sit and rest more often than the others when running or standing around with the others. She seems to stumble around a lot. While her feet look normal to me, she does kind of fold her toes together and sit back when she perches on something rather than resting on her feet like the others do. Is this something I need to worry about? If so, is there anything I can do to help? Thanks!