In my one year old perennial border, ONLY my 3 Veronica's (Evelin) look as if they are dying. No frost yet. The leaves first get dark (purple) blotches, then turns dark purple, then they are turning white and then the stems seem to die down to the root. It still gets new light green leaves and shoots and buds, but they soon start withering back too. No other perennials are affected (it grows next to a rose and Salvia) - oh, there is also a mint close by that seems a bit blotchy...

Is this a disease or the normal life cycle?