Phosphoric acid is the main ingredient of commercial rust removers. It converts the rust into a stable compound to prevent further rusting. It's typically used on rusted car bodies before painting. I like the ease of application of Naval Jelly (Available at Amazon, see link below). Hmmm - I don't see the link. No matter, just go to Amazon and search for Naval Jelly. That's Phosphoric acid in a jelly-like consistency so it will stick to surfaces while it works, instead of running off.

greg In the future, don't use soap. Regardless what ppl tell you and what you find on net, it is not the best to use it on plants. Soap will dissolve cuticular wax on the leaves, not helping the plant. Castile soap is made of olive oil, so it is safer to use on plants (but if purchasing, make sure it is vegetable-based soap, as Castile name is used, unfortunately, loosly...) Rubbing alcohol is enough for scale - but if you had to rub/scrub hard & also use nail, I doubt it is scale. Scale come off quite easy. Next time you see similar spots, test first if it is scale - take a cotton ball or tissue, moisten it and wipe off the 'spot' - should come off easy and if squished, you'll see blood...maybe gross, but at least you know what you need to do. BTW, were there any marks-damage left after scrubbing? (Edied to add: I just re-read posts and noticed that Crenda already mentioned possible damage on the leaves - that's what I was asking for).

I dont think you have anything to worry about the red marks, mine did that when it got a good amount of sun, the brown marks could be to much water, they like to be moist not wet.

The chief enemy of creativity is 'good' sense. Pablo Picasso Good sense if greatly overrated but it helps one navigate the mundane, without it who knows where one ends up -