We have been having some issues with eggs lately. Shell-less eggs, then a few days with good eggs, then nothing. One day one of my ducks laid just a yolk. It was broken when I found it and I don't know if it was intact when it was laid or not. Since then, sometimes there are yellow smears on an egg, what appears to be yolk. There is no sign of yolk anywhere else in the duck house/enclosure or yard, just on the egg, which leads me to believe it is being deposited on the egg while the egg is inside the duck. I have had 4 eggs with this yellow smears in the past 2 weeks. It washes off with water and some minor scrubbing. At first I assumed it was yolk, but now am wondering if it could be infection or something else - and in that case, should these eggs be consumed?