I was recently gifted a ton of new plants by mail from someone I met on another gardening site. Most arrived fantastically healthy. However, a few of them came with these rusty spots at the base of the plant with some lesions in the leaves. I have heard two different theories, mites and fungus, and many different ways to remedy both. I need some help figuring out which problem this is and the best way to combat it. Here's a bit of history about how I have cared for them in the short time they've lived with me-- I let them air out for a few days before potting them up (in miracle gro cactus & succulent mix with added perlite, as I tend to over-water sometimes). I didn't water them for a week or two after potting. They have been sitting on my east-facing back porch, which gets morning sun for just a few hours each day. I moved them to the front porch today away from the rest of my plants.