Lethargic Hen not eating

[Lady Badlands]

Sheelah died the day after we started giving her the medications. We think the medications were incorrectly prescribed because our rooster had an abscess lanced at the same vet appointment. The vet had us giving Striper the same antiobiotic and he started to get sick, just like Sheelah. We took him off the antibiotic right away, but he doesn't seem to be improving. This is really confusing.