Duck limping no visible injuries

[JenQ92]

Hi! New here. I noticed two days ago one of my ducks limping. We've checked both of her legs and feet and can't find any sign of injury. She's also been doing this sort of quivering thing with her mouth, I guess kinda like she panting. Anyone have any ideas of what could be going on or if there's anything I can do to help her?

I tried uploading a video and was unable to

 

[Yardmom]

How old is your duck? What are you feeding it including treats and supplements?

 

[JenQ92]

6-7 months? We feed them scratch grain, layer pellets and the occasional fresh fruits and veggies.

 

[Yardmom]

Some owners say ducks especially larger ducks need extra niacin even when they are grown. I have not had an issue, but my ducks are free range along with their pellets.
In sufficient niacin could cause leg issues.

 

[HereForTheChicks]

Try a high protein diet for a few days