Moby, I have an After Eight that looks exactly like the one you show with the dark--almost purple leaves. It did the same thing last year; the leaves started out like yours but in a short time turned yellow and dropped off yellow and it went into premature dormancy. So, I moved it into an isolation bed as a clump last Fall. This year--the same thing--nice green then here come the dark purple leaves. So now, since I have lots of After Eights and can afford to experiment: I'm going to dig it up, save the dirt for analysis, wash and inspect for 'whatever' I can find, and then either replant or discard. I don't think its frost damage because that usually results in those unsightly brown leaf tips only. I'll 'edit in' a picture later today of my plant.
EDIT: Pictures added: 1. Example. 2. typical early frost damage.
