whose sister? the drakes that you rescued but he wants to stay with you and Brownie your duckling? do you not want him any longer? Sorry I am confused.
Do you keep the lights off overnight? If you don't I would so your not disrupting her sleep. Ducks need other ducks they are flock animals so she is lonely maybe eventually your drake will accept her.
It's lonely can you get it a friend? a safe mirror can help too and a stuffed animal. But a friend is what it really needs. Has your Muscovy befriended it?
Feed and treats look good. How long has the duckling been breathing like this? any discharge from nares or eyes?
How is your chicken that was having problems?
does your duck cough?
Your rescue looks so much better I am glad to hear he recovered. As for your 7-week-old what do you feed and are you giving treats and supplements? usually, mouth breathing is from being too warm but can also mean respiratory illness. Is the ducking eating your dog's food. My ducks love dry...
Is she still laying eggs? yellow discharge can be from an egg breaking inside of her but what did the discharge look like that came out of her nose? Was it clear or did it have color to it?
He must be injured in his neck was there any wound on his neck Maybe a bad sprain? They can be painful. I am not sure there is much that can be done other than what you are doing. Taking care of him and supporting him through this.
here is info on other pain relievers...
That is great news!! he needs a way to safely get into the pool a ramp or steps made out of scrap wood would work. But it would be better for his legs not to have to jump off the side. The reason saying is my Muscovy drake injured his legs jumping off the side of the pool so best to keep that...
How does his wound look? can you get a picture of it or them and is there any smell or oozing he may have infection. Of course if the dog grabbed him his body is most likely very sore but the only thing I can think of to get him to eat is tube feeding we have info if you want to try but you'll...
All I can do is give you this I am not expert on meds
https://poultrydvm.com/drugs/carprofen. Is he showing any improvement? where do you think there is inflammation?