Pullet can barely stand and walk, tail down, she sits while eating

[Pufna]

My about 8 months old Jubilee Orpington pullet is acting very weird for about a month now. I gave her some vitamins, antibiotics, but nothing seems to help.
It's very hard to describe how she acts, basically she can make a few steps before falling on her bum, her stance is pretty low. Other than that she eats normally, although while sitting/laying most of the time.
There's a thread on here where a member posted a video of her hen and its pretty similar with my pullet, here's the link to the thread so you can see the video of how she acts:
https://www.backyardchickens.com/threads/hen’s-tail-down-sitting-often-help.1332572/

 

[azygous]

Try giving her B-complex every day, one tablet into her beak without crushing or diluting.

If she continues to worsen instead of improving after three or four weeks, you should suspect either Marek's or Avian leucosis.

 

[Pufna]

Try giving her B-complex every day, one tablet into her beak without crushing or diluting.

If she continues to worsen instead of improving after three or four weeks, you should suspect either Marek's or Avian leucosis.

Thanks for the help, will try.

 

[Jen1131]

Any update? I have had a similar issue with my chicken same age