I just finished a long day - sorry it took so long, but I was not near a computer. I don't want to worry you unnecessarily, but ducks hide illness, and she may be in serious trouble.
Has she laid any eggs? Who else is in the flock?
I would get her into sick bay - some place I can check frequently, where she is confined, safe, on clean bedding, with fresh water and food.
There are a number of things that could be happening. Injury, infection, parasites, egg yolk peritonitis.
I would:
-give her a lukewarm bath deep enough to float in and observe closely, to look for clues. Her breathing, how she moves, any odd odors.
-put a teaspoon of charcoal per pint of water in her drinking water for a few nights.
-get a poultry vitamin with electrolytes and probiotics into her daytime water for a day or two.
-get antibiotic, like Duramycin or Tylan. I know for my runners, when the vet found a suspicious looking microbe in a fecal sample, we gave them 1/4 teaspoon of Tylan powder per liter of water in their nighttime drinking water for seven days (couldn't eat the eggs for ten days). I
think it was Tylan50. From another thread, someone recommended (for possible spread of infection from bumblefoot to the rest of the body)
Duramycin-10 at 1/2 tbls. per gallon for 7-10 days.
-give her treats or whatever she will eat, as frequently as you can.
-let her know she is loved
-bring in a buddy if she is very anxious about being alone, but be careful with the antibiotic, then, that's a wrinkle to think through
