I woke up very early this morning, to find her dead. Thank you every one for the help and suggestions. It is just amazing how quick it all happened. I thought this duck could survive anything. She lived through a possum attack, and a dog mauling. (Those both happened a good while ago...nothing recent)
She will be missed. Most of all by our male who never left her side. He was laying quietly next to her when I found her. I just hope the over two don't get what ever she had. They are showing no symptoms so I am taking major preventative measures now.
Again thank you every one. I appreciate it, this is the first duck I have lost before, so it is still kind of a shock.