I'm wondering about rickets...an illness where they cannot process calcium to make vitamin d...pls look it up as I'm sure I slaughtered the definition...anyhoo my pullet had issues with her leg(s) where she would high step like she was walking over a downed stick w/each step, which progressed into getting wobbly and using her drooped wings to balance, which progressed into what seemed like partial paralysis of one leg. The leg was not paralyzed, she could move it but it was like she lost motor control of it. It would stick straight out behind her similar to what people refer to as 'the mareks pose' and also walking very wobbly in the top of that foot w/her toes curled under. During the course of her progression I tried a few doses of aspirin fir possible inflammation, hypericum (homeopathic st. Johns wort) because I thought it was possible nerve damage, vitamin e, polyvisol w/o iron, spinach, all to no avail.
I am seeing vast improvements w/a recipe I found on BYC for rickets. It's foods you probably already have in your house. She has started walking flat on the bottom of her foot like normal, taking a few steps at a time. I'm continuing the diet. I also added a tablet of vitamin D and drops of polyvisol to each feeding.
If you have ruled out mites, worms, broken legs, slipped tendons, painful bumblefoot infections, etc. I would try the rickets diet. Let me know if you want to try it, I can give you more details on it. I would still separate her and give her a heat lamp.