If you don't have B12 some Karo syrup given orally can also be a perk them up. You only need a tiny amount (1/2 a drop or less) placed in the mouth. That's the only thing I give orally to a sick animal.
At this point you've gotten many suggestions and opinions. Now for the hard part. Sifting...
My catch all is some B12 and Naxcel or Pen G. I'd have to look up the dosage. They were given SubQ or IM. Then move the ailing animal, (chicken, goat, or rabbit) inside to a small crate in the warmest part of the house.
How long has she been off the Tylan? Did she ever perk up on it? Where are...