At the moment I don't have a car available (I will in a week or so) and the poultry vet is some distance away. I'll take some photos and email them, the vet lady has been very responsive in the past. We have some leftover liquid antibiotic from Junior's recovery adventure and I've ordered some sticky wrap and Vetericyn online.
It's unusual to me how the limping duck will sometimes limp strongly but at other times keep up with the group as though there are no problems, and climb into the pool with the limping foot first. The climbing part, in my opinion, suggests that we're not dealing with some joint or bone problems since pure physics would not allow it.
Also her general behavior has changed, and for the better - when this happened on Tuesday she was obviously feeling hurt and endangered, she spent most of the day hunkering down in the grass, hiding in the bushes, not coming to the water and food stations. That's why I decided to keep her in a crate for a couple of days so we see that's she's been eating and drinking. She has now been free-range again in the last 3 days and yesterday and today I can see her eating and drinking with the others.
So it's really not clear to me where all this leaves us. At the very least things are not getting obviously worse.