Don’t worry, it’s just water deposits. :)

I also had hard water spots all over my plants leaves. We have extremely hard water. I tried everything to clean them. The only thing that worked was an accident. I have an ongoing problem with scale and spider mites, so I wiped down all the leaves with diluted alcohol and then sprayed with Horticultural Oil. Now my leaves are so green and shiny!

Thanks, Alanna! That's really helpful info. Glad to hear your tree's leaves actually look better post-pest problem!

Since it has been determined this isn't an urgent matter I'm going to leave the tree alone for now (as hard as that is for me to do!). I think it's been struggling enough while I try to figure out how much water and light it needs and I don't want to add to its stress. Perhaps when it's happily outdoors in the late spring I'll do some more experimenting.