Duck is limping, what is the issue?

[Reuboid]

So recently one of my Rouen Clair ducks has started limping. She is the bottom of the pecking order and is quite light. I have taken photos of her legs if anyone can identify the issue it would be appreciated. We are taking her to the vet soon but if someone can find the problem I would be very pleased.

 

[Miss Lydia]

Did you check for thorns or splinters? Is that swelling in the left leg right above the foot?
Is she being allowed to eat? being you mentioned she is at the bottom of the pecking order is light. Do you have more than one feeding and waterer set up? Could she have jumped out of the pool and injured her leg? Is there bumble foot? I do see some places on her foot that make me think it could be starting?