@GGBEAR Hi!
She could have a nervous system problem, or there is a tiny possibility she is presenting herself for mating. When does this happen? When you or the other duck are close by or not? I would get them both on some B vitamin supplements. Use the B3 (niacin) in the supplement to gauge how much water to add. Aim for 150 mg niacin per gallon of drinking water. It should be fine for both to take.
As an alternative, put a tablespoon of brewer's yeast (not baking yeast) per cup of food for a couple of weeks, see if she improves.
How old are they? The B vitamins do the most good for younger ducklings, but if she's deficient, you may be able to help with that.
What is sku wif? Does it mean oddly?
Seems to me both have had too much attention from drakes. There may be spinal injury, internal injury, pulled muscles, as well as the pulled neck feathers. So, I would be aiming for spa treatment for these girls for a few weeks. You may have rescued them from a very rough time.
Spa treatment: The B vitamins as above, and daily time in lukewarm water deep enough to float in. Just let them relax a bit, take weight off their legs, stretch and move. Toss a few treats in the water with them. Keep them safe, always. Everything wants duck dinner. Keep them where they don't get too hot or cold. Feed them a well balanced ration, plus some fresh vegetables especially greens (not much spinach). Chat them up - tell them stories, just let them know you are giving them some gentle attention. Sing, if you want to, mine like being serenaded.
If you can, you might consider a vet - but for many of us this is not possible.
Keep us updated, and check out the archives on BYC. Good nutrition, rest, low stress, swim time, can make a world of difference.