The second, fourth and second plagal tones all use the soft chromatic scale.
British Dictionary definitions for plagal
(of a cadence) progressing from the subdominant to the tonic chord, as in the Amen of a hymn
(of a mode) commencing upon the dominant of an authentic mode, but sharing the same final as the authentic mode. Plagal modes are designated by the prefix Hypo- before the name of their authentic counterparts the Hypodorian mode