Since you started Tylan, it can be given for 5 days, so nothing wrong with completing the dose. Dosage is 0.2 ml per pound of weight 2-3 times a day for 3-5 days, and I like to give it orally, so it does not damage the breast muscle.
She doesn’t sound like she has a respiratory infection, so I would stop the antibiotics, and give her some probiotics for animals, or a tsp of plain yogurt with cultures in her food daily to get her gut bacteria back to normal.
With leg weakness or curling of toes, it is good to give a poultry...