[Marigoldsfail21]

Well I took a closer look at the plant and now I know what it is. I saw that some of the little specks were moving around, so I'm assuming that they're some sort of mites. They're orange-colored and a lot smaller than any other mites I've seen before, which is probably why I missed them when I examined the plant earlier.

I'm keeping the plant isolated in a plastic bag for now. I'll take the plant out of the pot later and wash it before planting it in some fresh soil. I'm hoping that will take care of the problem.