Does anyone know if Buddleja's get sick? I've a got a Buddleja which is developing yellowing leaves, the blooms are dying off quickly and yet its still growing new growth. I ignore this plant water evey so often, lots of sun and evening shade, I've also noticed that there is somewhat a powdery mildew substance on the stem of the plant not the leaves. Could it be an infestation of some critter, or its just telling its slowly dying and just to leave it alone? So I'm asking anyone who might know.