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If they have been in the brooder, I doubt it's worms.
If you ever think it might be, have a fecal test done.
If you can get the to the vet, I would.
Could you review what they are eating, how big is the brooder, the temperature, how often they get swim time (supervised), any of that.
Loss of appetite is serious. They may have picked up some kind of infection, or need supplemental nutrients.
Edited by 4aylesburys - 4/14/16 at 2:35am
At a month old and being inside, they likely won't need supplemental heat anymore.
Are you adding niacin to their water or food?
What is the protein % of their food. The first few weeks when they are really growing like weeds, a high protein is fine, but beyond that, it can cause some issues (usually seen as angel wing).
With their snacks, are you providing grit or getting them outside time so they can get some dirt to help with the snacks they are eating?
I'd start adding niacin to their feed or water. Leg issues are usually a sign of Vitamin B deficiency and can usually be easily corrected with added niacin.
If your other one isn't eating - is the crop full? It shouldn't be if they've not eaten.
When feeding anything other than their crumbles, it is best to offer grit or have them outside so they can get their own "grit" from the ground.
Depends on the weather, about putting them outside. I used to get chick grit and put a tiny sprinkle on their food - Storey's Guide to Raising Ducks recommends this.