Ok, just spoke to the vet. I will try to make this make sense.
It was pretty much her heart. From the way I understood it, her body was starting to shut down. She was not broody but just exhausted. What was odd was that there was absolutely no evidence of egg production anywhere. Nothing forming at all. She was only 3. So, between the fact that she was fairly young and the time of year, it was strange that she had totally stopped producing eggs at all. All her other organs were healthy. But her heart was working so hard she just was too tired to do anything, including eat. There was nothing in her intestines or stomach, so she had stopped eating. I did see her eat a bit here and there and assumed she was eating just when I was not around. The vet did say while the heart thing was probably something she had all along, that it had only gotten worse very recently. Because she had not lost much weight. There was a lot more to what she said, but it is difficult for me to remember so this is the gist of it all. She was never a real healthy looking bird, but she always acted fine, very active and normal. But the fact that she always looked a bit "off" is probably tied into her heart issues.
So, all in all, there was nothing I could have done for her. It was not reasonable to expect to put her on heart meds. I did not raise her from a duckling and she was not easily handled, so any medicating would have been a struggle for both of us and would have put more stress on her. The vet said I made the right call letting her go, so that is a small comfort.
I know she had a nice life here. I don't know what her early life was like, but I want to think she was happy here with her flock, she had plenty to eat, plenty of water to drink and play in, and free range on the property most of the time. She had a dry place to go to get out of the elements and I found her inside more than any of the other ducks. Hindsight being 20/20 maybe that should have been a clue, but I guess I missed that one. I feel bad for that, but don't know what I could have done at that point. She was normal otherwise.
Ugh. This rots.