I sure hope it helps. Update when you can please.
Heres the info we have here on BYC
https://www.backyardchickens.com/threads/heavy-metal-poisoning-in-ducks-no-appetite-falling-weight-loss-lethargy.873138/
I am so sorry she is going through this and you too. It's so hard to know how to help them. I wish I knew what to tell you to do to help her. Any chance she could have eaten metal?
If at all possible you might want to take her to the vet. Gently run your hand up and down her neck to make sure she hasn't something lodged in there. Is she eating and drinking normally still?
Is she showing other symptoms like discharge from eyes or nares. listen to her breathing.
Something is not right. Since she is eating and her poop looks normal I really don't know unless at the creek she may have eaten something that has her feeling not so good today. Lots of things down around water even a dead fish etc. There are flushes for this I can give you the info and let you...
Okay well we can rule out egg laying trouble. Anything around that she could have eaten that is toxic plants water dead mouse etc? Beautiful Rooster by the way.
{Has she been laying?}When did she lay last? when one of mine is going to lay a soft shell she'll go off by herself and it takes a good while to get the egg laid not long after she is back to hanging with everyone and acting normal again. It seems to be hard on them to lay a soft shell.