"下午好，各位老师"用英语怎么说？

“afternoon, teacher！”完全可以表达出你的意思.
赘述是负担,teacher前加every，each个人感觉说教味道太浓.

Good afternoon,honorable teachers!
译为：下午好，尊敬的老师们！

Good afternoon
Each teacher

按你原文翻译的

“Good afternoon, teachers！”这是最地道的表述！
赘述是负担,teacher前加every，each个人感觉说教味道太浓.

Good afternoon teachers.

good afternoon every teacher