My coreopsis (I believe it's "polaris") that I planted this spring is looking a little tired, and when I peeked at the roots (it's a bit flopped over), a bunch of crawly worm things peeked back. I came back and snapped a photo of a few that didn't hide very well. Are these millipedes? Should I do anything about them? I don't like to use pesticides in my garden, but I could dig up and dispose of the plant if it is warranted. I appreciate your wisdom!