Can't help with what's on the ceiling, but suggest checking the attic for leaks.

Did you ever figure out what this was and how did you treat it?

do you have it now mmw? i hope it does not spread, perty yicky looking.

I have the same thing. It may be mold growing through the drywall from a hidden moisture source. These spots appeared almost simultaneously, some smooth brown, some crusty white. Most likely feeding off an organic filler in the drywall and a source of my respiratory problems. I sometimes need to leave my windows open for my symptoms to disappear.