I've had this plant for a long time, and for most of that time it was outdoors, in a shared area with other plants and heavy sun. It didn't do well, so I dug it out and put in it's own pot, with a little less sun, and it seemed to thrive- it tripled in size and even put out, occasionally, tiny red flowers.
But lately I noticed that it has a layer of an icky white substance on it, and it isn't doing so good- dropping leaves and no new flowers.
What is it? What can I do about this?
Here's a picture from up close: