Hi there folks! We have 27 li'l three-four week old ducklings of various breeds, we know we have several runner ducks, one itty bitty mallard, a few blue Swedish, pekings, and for the rest we are stumped. One of them is so skinny compared to any other duckling, he seems fine, eats and is active as the others, should we be concerned? They ones that we know are runners are even bigger, but I do think this li'l fella is a runner as well. Any ideas or help would be appreciated.