If you're certain it isn't evaporated steam from the shower, mixed with a bit of dust to turn it brown, the other main possibility is "surfectant leaching"—the paint separating because of how it was first applied
Learn how to fix and prevent the appearance of paint streaks, spots or residue on painted surfaces known as surfactant leaching.
After reading that article I think you’ve nailed it! This seems exactly like what’s happening. That wall must have been repainted and dried under less than ideal conditions. Thank you!!! (It was really starting to creep me out!)
This is the closest thing that seems to make sense so far! Thank you! I'II look into it... the weird part is it's not happening to the same paint on any other wall in the room. But maybe there was something different about this wall.
I am painting our bathroom today! This couldn't have popped into my feed at a better time. Thanks!