It does take some time to recover from it, and they are weaker from it also. I wouldn't stop the treatment, but would keep a close eye on your bird. As Freds Hens said, he might not make it even with the meds. Sometimes, they are just too far gone. But it could save the rest of your flock. I am praying for the best and hope your bird makes a turn around soon!!! Did you try tipping some of the medicated water into some feed for him? That seemed to work well for me, to get it into mine faster, even the ones not eating gulped it down....or the dropper to jump start him?
Best to you!
Best to you!
