What is this on my birds nest fern? It was in a sort of sorry state when I got it from the grocery store 4-5 months ago. Since then it has been repotted into chunky soil and growing good new leaves. After not looking at it for a week or two; I come to see this in it. What is it? App says spider mites, but I don’t see any webs, or anything crawling around! What do I do?



