What you have is surfactant leaching and it comes from the surfatants that are in all acrylic/latex paints not being evaporating out of the paint as it dries. The surfactants normally evaporate out but if the moisture in the air is high during the curing period they just sit on top of the paint and they do not hurt the durability of the paint at all but do not look good. They can be washed off while soft with a mild soap and water solution. You do not want the surfactants to dry and harden as then you will need to prime over it with an oil based primer and repaint. I tell people when they are painting a bathroom to try and not use the shower in that room for a week after painting to not have this happen.

Good call 5! Not too often you see a surfactant leach inside!

Perhaps a dark colour? High colourant loads can make that more likely to happen.

Mr. Paint