Do you notice any brown, raised bumps on your plant? If not, no need to worry, I just know scale can excrete a sticky substance.

Planto

No bumps. What should I do if it gets scale? Thanks much!

I actually had the same thing on one of my sedums, which also has an infestation on aphids. I was just reading that their droppings (it's called honeydew) is very sticky. So, check your plant for aphids. Maybe that's what is going on? I took a screenshot of a photo off Google of a leaf with Honeydew on it. Hope that helps! - Sam :)

Thank you.