Skinny Runner Duck! Need Help, Please!

[bugheadmomma]

Hi! I have three indian runner ducks, three buff ducks, one rowan duck, and two pekin drakes. All ducks are right around one year old. In the past five days, one of my runners has stopped eating or at least I haven't been able to get her to eat in front of me, even when I offer her favorites (cucumber, tomato, mealworms, etc.) She was always my best layer, but the entire flock hasn't laid a single egg in five days (it has also been very very cold and just warmed up today). She is getting ridiculously skinny and she is staying away from the flock. When I let them out of their coop in the mornings, she comes out and walks around, but then I find her on the opposite side of the house or back in the coop all on her own. She still allows me to pick her up and she is walking just fine. She's just so skinny. She was always a thinner duck, but now it is scary how thin she is. She still runs, quacks, etc... but I've also noticed over the past 48 hours she isn't preening. Her feathers are starting to look awful and like she doesn't have as many as the other ducks and she has a ton of new feather she isn't doing anything with and looks like she did during her first molt. She happily played in the tub a few days ago, but afterwards did nothing to preen, so I had to keep her in the bathroom with her sister until she fully dried and I could return her outdoors.
I don't know what to do with her. None of the other ducks seem even a little off, other than not laying, and they don't seem to care about her even though the ladies all stayed together until five days ago. My drakes are also trying to mate her constantly so I'm having to keep them in a separate yard when they are out free ranging to give her some peace (drakes have been separate for three days). They aren't trying to mate anyone but her and this is also new (even though they've always preferred the runners for some reason). Any idea on what might be wrong? Anything I can do?

(We don't have a vet within four hours willing to see a duck, so I'm trying to do what I can without a vet unless its an emergency since the car ride freaks them out horribly and it costs more than I currently have to spend. I love my ducks, but I also need to feed my kids and I'm alone now after my partner passing two months ago. Please don't judge me too harshly for coming here first. I am trying to do my best by the ducks.)

 

[nuthatched]

Actually, more often than not, BYC IS a much better resource for bird wellness than a most vets, much cheaper too.
Sometimes you need a vet but there's typically enough knowledge here to accurately determine the issue and treatment.

What is there main food? I know ducks don't usually need worming but it might be worth a shot.

 

[bugheadmomma]

Their main source is a pellet feed, but I add veggies, fruits, and mealworms… along with them foraging through my yard and garden constantly.