I'm hoping that someone can help diagnose what is wrong with my rose.
Last year I planted this David Austin climbing rose called Madame Gregoire Staechelin. See link: Mme Grégoire Staechelin - David Austin Roses.
Our soil type is heavy clay, so I spent considerable time digging in plenty of organic matter and horticultural grit before planting. This improved it greatly. On planting I also used the root grow mycorrhizal fungi. The rose grew well for the first couple of months last year, but then quickly plateaued out for the majority of the summer, despite being fed and it receiving 6-7 hours of sunlight. This Spring I treated the rose for Blackspot & fed it with David Austin rose food in Spring, I also bought Uncle Tom's Rose tonic to use as a foliar feed spray. After the Blackspot cleared up, the new growth looked fine, but now the ends of the leaves are turning brown and curling up. I also can't understand why it has such poor vigour.
Can anyone explain what this might be and what I'm doing wrong?