Not long after my last post, it quit raining regularly. Exacum shriveled up.
My mystery plant did end up being a Physostegia, just like Stone said. But not obedient plant, the only Physostegia I knew about. It's false dragonhead, P. digitalis. I really love it! It's blooming now, when not much else is. The bees love it.
Soon it will be time to spot winter plants starting to come up for their season.