Did you try scraping off one of the small darker colored dots, or one of the larger brown ones? The large brown ones look a lot like scale to me, the smaller very black ones look different, maybe damage from the scale. I would try scraping off one of the larger brown ones, if it is scale it should come off easily (if scraping it off seems like it will damage the leaf then it isn't scale). I circled one of the ones I'm talking about in your picture so you know which ones I mean.
Another question, are there any clear droplets on the plant that feel sticky? This is another sign of scale (it's called honeydew, it's scale poop
)