A few months ago I had scale bugs on a different houseplant in a different room and asked about them in a different SE site:
Looking under a low power microscope I also found some flat waxy like white deposits on the undersides of leaves that seemed to show other stages in the lifecycle, something that appeared to be hibernating/transforming, and much smaller, very tiny little black crawlers only visible in the low power microscope.
Today I found these irregular but mostly circular white, waxy-looking spots on the TOP sides only of a few leaves of this houseplant.
I occasionally give this one a direct dose of sun (as shown in the last photo) but mostly keep it in a moister, indirectly lit area. I also often water it using a plastic squirt bottle from a distance of a meter or two, so it frequently gets splashed on the top leaves by tap water.
So I'm wondering if maybe my tap water and/or plastic squirt bottle have stuff in it that forms these white spots when the splashed water droplets dry, but still I'm panicking, so I'd like to ask:
Question: What are these whitish deposits on the top surfaces of these houseplant leaves and should I do something about them?
Click any image for full size:
UPDATE Here are new photos
since three more plants have suddenly exhibited the same whitish spots overnight, and squirt bottle I've been using for the last few months