I'm not sure what's going on with my Lilly Pillys, but they are developing whitish-grey patches on the leaves. I've looked at them under a magnifying lens but I cant see any insects that may be causing this. I also tried wiping/scraping it off, but it seems like it's embedded in the leaf itself so nothing comes off. I don't think it's powdery mildew. Can anyone help me identify what's going on here - and how can I treat them?
