hi all, i have nine three wk old muscovy ducklings, they are all growing and eating very well except one... that one is now only a third of the size of his/her siblings and is not eating very well, its belley feels like a baloon and it hardly eats anything. Its head is 'gaunt', for a lack of a better term, with the eyes bulging out and barely any flesh on her face. What should i do? It still walks and runs with the rest of them, but when then eat it just stands there... please help. Thanks for your time!!