I don't know anything about gardening but I have a small patch of gravel out front where I like to keep some potted plants. My acer's leaves came back healthy after winter but as you can see it isn't doing too good now. I thought the crispy leaves might be because I let it dry out (I was ill for a couple weeks when we had some dry, sunny weather), but looking at the base I noticed this white stuff: https://i.imgur.com/2qc87P3.jpeg, not sure if it's scale or something else? Any ideas what I can do? I see a fair number of tiny bugs and ants in the soil but I'm not sure what's normal. I'm located in the UK, if that matters.