I have a duck that has started to lay shell-less eggs for the last week. She is a Gold 300 hybrid layer a couple of years old and has been laying for almost a year now (forgot to molt last fall). All my other birds seem fine and the others that are laying are continuing to lay regular strong shells. I provide layer pellets, waterfowl feed, oyster shell, and grit. All separate and all available all the time. They free range during the day so plenty of sunshine (Vitamin D). She had been laying slightly odd shells for awhile but I had a hard time figuring out which duck it was until she laid the shell-less in front of me. I have now seen a few of these shell-less ones now. I am thinking its possibly an infection. She is alert and active but a bit thin. I have been supplementing her with a bit of dog food and a bit of brewers yeast to help her gain weight. She looks healthy in every way except that she is a bit thin and needs to molt, and is now laying the shell-less eggs. Any suggestions? Any ideas on what could be causing this?