Later: I went out and planted a few bulbs. A bag of Oriental lilies came, and I still need to plant those. I clipped the grass around the raised bed and around the purple coneflowers. I weeded around the plants by the front porch. I picked another broken tulip.
Retrospectively: Mystery broken tulip # 2 was reddish brown or mahogany with little yellow streaks. I left that to grow on the hillside. Mystery broken tulip # 3, which I picked, started out as a red tulip with little yellow streaks on the outer petals, but the yellow expanded into much larger streaks, with big patches of yellow on the inner petals. It sort of reminds me of a 'Ketchup and Mustard' rose, but prettier. The folks at the nursery agreed with my thought that it looked like a 'Ketchup and Mustard' rose in the coloring, and suggested that maybe it was a 'Couleur Cardinal' or other red tulip that I'd gotten in a previous year that had broken. Two of the 'Couleur Cardinal' roses that I'd planted lower on the hill in 2017 or 2018 did come back this spring, but they were of the color and type they were supposed to be, with no breaking. Mystery broken rose # 3 is closer to where a couple of 'Rococo' tulips came back from the same year that I planted the 'Couleur Cardinal' tulips, but the petals of the broken tulip are a standard oval shape. It may just remain a mystery.