bruising on goose webbing?

[wildharvesthomestead]

can anyone tell me what's going on with my goose's webbing? she's had this on and off and it doesn't seem to bother her and goes away on its own. looks like bruising and fades over a few days like bruising. nobody else has it, and she has it way worse on this foot than the other. google isn't much help. I'm in upstate NY so there's nothing around that could have stung her, and she has this across both feet, though the left (pictured) is always by far the worst for some reason. thanks in advance!

 

[Goosebaby]

How old is your goose?
What kind of feed are they on?

The closest thing this reminds me of is excessive cold exposure, maybe she’s more sensitive to cold than the others?

Beyond that I would wonder about some sort of circulatory issue. Does she sit around a lot or breath/pant more heavily when exerting herself than the others?