I don't know what is wrong with my Clematis this year, I have three, they have grown to approx six feet tall but the bottom two- thirds is all brown and papery ! They are in pots, I have fed them but wondered am I over/under watering. I haven not treated them any different to any other year but they look awful. Two have given out a couple of small flowers. Do you think they are frost damaged or something? Should I cut them down? thanks in advance.