I have a female pekin duck that is about a year old. She has recently started looking thinner than the rest. I have noticed she barely eats anything. She still walks around with the other ducks, swims, drinks, digs around in puddles when I water their area. I have put food in their water so she at least gets some nutrition. What else can I do? I am really concerned since it has become noticeable that she isn't eating and losing weight.