The phrase "were business" can be interpreted in a few different ways, so here are a few antonyms depending on the intended meaning:
1. If "were business" is taken to mean "were serious about something," some antonyms might include: casual, lighthearted, unserious, frivolous, or flippant.
2. If "were business" is interpreted as "were engaged in commercial or professional activities," some antonyms might include: leisure, relaxation, pleasure, hobby, or non-work.
3. If "were business" is understood as "were involved in something underhanded or unethical," some antonyms might include: honest, straightforward, ethical, moral, or principled.
Regardless of the intended meaning, the antonyms for "were business" generally suggest the opposite attitude or activity.