Ducher

I planted my Ducher in a large pot with fresh nursery rose specific potting soil it gets plenty of sun and it has bloomed a few times it is healthy in some parts of the bush yet some branches have a black line up the bottom side of the branch then turns completely black and dies I cut the off at the base I called andthey would not connect me to a staff member who could counsel me on what to do I am afraid it might die and I will have to ask for a refund