Limping duck and what food to feed once ducks are laying eggs

[Flik168]

I have a duck that I noticed has started limping on her left leg. She seems to still be walking around and eating ok, but has been limping. She is a Rouen and is about 4 months old and there are two other males and two other females in the pen with her. I'm wondering if this is just a sprain and will heal or if something else is going on and what to do about it. I'm thinking it might just be sore or a sprain, the male ducks are sometimes rough with the females so maybe they hurt her a little. Anything I should do about this?

Also, my ducks are just starting to lay eggs and I was wondering what kind of food others use for long term food for the rest of the ducks lives. I have been using Purina Flock Raiser the whole time so far but I didn't know if this food is good for the ducks long term or just while they are growing. I know someone who uses something called Scratch & Peck for food for her ducks and chickens. What do you think of that food?

Any advice on these things would be great. This is my first time owning ducks so I don't quite know everything I should do yet.