She could be Buff Orpington or a Pekin so she came as a mystery duckling? From where? Have you looked at the hatcheries website at the ducklings to see if you can match her up? She sure is a pretty little one and looks very healthy. I know many will post on here usually in spring when their ducklings are arriving that their Pekin will mouth breathe even without heat. I don't know why this is but we usually hear of it more with Pekins. Make sure to supplement with something like Nutritional yeast or Liquid BComplex at the age they are they are growing so fast they can sometimes end up with a niacin deficiency which can cause lameness. Other than that I would just keep an eye on her if she is eating good and not isolating herself from the rest ( which usually means they are sick) then hopefully she'll grow out of this. Her heart beating fast most likely from you picking her up. But if you continue to be concerned then possibly an avian vet would be the next option.
Please keep us updated.
To me it seems her eyes might be becoming swollen, or I am just paranoid.
