I recently purchased a handful of young Running Serviceberries (A. stolonifera) online but soon after they started to bounce back from shipping I noticed these rusty colored spots on them (almost every leaf of all five plants). Each spot consists of a cluster of smaller slightly raised orange dots, and they don't wipe off or spread when I rub at them with my finger. Keen to know what I've got here - is it something that risks spreading to other plants in my garden?
I thought it might be fungal rust but the guides I found online say that the rust spots from that should wipe off easily, as they are just spores. These spots don't seem to do that.