I have a rose, 'Poulsen's Pearl' Poulsen 1949, growing in a container 14 x 14 x 16" deep. It blooms ok, but the leaves are yellow between the veins. Both new and old leaves are this way, but the new leaves especially so. I was told there was not good enough drainage, so I moved the pot up so it drains easily and that helped for a while. But now the leaves have turned yellow again. The soil is from the garden with much clay mixed in with organic matter. The rose behaved very well in the garden with this same soil. It's been fertilized with Rosetone in spring and Peters 20-20-20 diluted 1:2 in July with no improvement. A cutting from this plant, rooted, and planted in the garden soil is doing very well. What[s wrong with the container grown plant? How can I fix it?