Female Muscovy Squeaking and Sleeping

[LazyBirds]

I have 2 indoor female muscovies. Recently one of the girls has been sleeping a lot and seems disinterested in things. When she is excited, she seems fairly normal but she spends most of the day sleeping.
She will eat if you bring food to her, but won't get up to get food very often. She's usually pretty excited to eat and will run over to her food.
She seems to defensive. She's picking on her sister more than usual and will sometime poof up when you approach.
She is chirping or squeaking like she's broody but we haven't allowed her to keep any eggs to roost on and she doesn't lay in her nest, she just lays down wherever.
It's been 6 days since she last layed and egg and I don't feel one when when palpating her underside so I don't think she's egg bound.

She doesn't seem to be losing weight and her stool is normal. She had some dark/black stools in April for a few weeks that made me suspect she ingested metal but those have passed. We went to the vet for a checkup on April 25th and the vet seemed concerned that the ducks were overweight at 4.8 lbs but had no other complaints about their health. All they did was a physical exam.
Edit: this is what her most recent poop looks like. It has a strong sour smell. Any poop experts out there?

 

[Miss Lydia]

Sounds broody to me. I have Muscovy and mine act similar when broody but they do come out to eat swim and poop 1-2x a day but squeak and puff up when they are out among everyone and will pick on someone if they get to close. Most everyone knows to keep a safe distance.

 

[LazyBirds]

Would she still be broody with no eggs?
Wouldn't she brood in her nest as opposed to just laying down anywhere?

 

[ruthhope]

This is my son's female muscovy when she first went broody this year
She is laying most days in her nest box but not sitting on the eggs. She has made a nice nest in her nest box in the coop but she also hides in the bushes for much of the day.

 

[Miss Lydia]

Would she still be broody with no eggs?
Wouldn't she brood in her nest as opposed to just laying down anywhere?

I have a broody Muscovy right now I took every egg she laid [can't have more than one Muscovy drake ] and she is still brooding in her nest.