Kathy where do you buy your Baytril I need to order some mine is out of date.This person just went through something similar, though her's never really lost it's appetite. Her story starts 10-30-14 at post #9:
https://www.backyardchickens.com/t/846873/please-help-with-sick-peacock#post_14278710
Between then and December 13 she tried a low dose of Tylan like you did, Corid, Safeguard, a high dose of Tylan and then finally she tried some Baytril that I sent to her. Her chick has gained lots of wait and is now 100%.
-Kathy