I went out for one last check on the ducks last night and found 2 shellless eggs. One was a normal size and one was just a yolk. I had already gotten one normal egg from them in the morning. Being that I only have 2 hens where did 2 shelless ones come from? I added some oyster shell to their feed to help out the problem. Being that they are new to me ducks I don't know if they had been getting it or not.