I set 12 duck eggs just 5 days ago. When I came into the house today, the smell was awful! I candled them and immediatley found the stinker. It was a white duck egg and the stinker egg looked black under the shell. When I candled it, I couldn't see anything. No light passed through it. Is it common for them to stink after just 5 days or did I get an old egg?