Fungi that thrive on dead materials (like mulch) tend not to infect live material, and vice-versa. Often they can survive on either, but only thrive on one. Yes, that looks like a slime mold - nothing to worry about. It often creeps up live stems, but rarely does any harm.
My neighbor here in St. Boni had more than 6 inches in his rain gauge from those storms a few days ago.