The leaves of my clematis (jackmanii?) are turning a golden yellow color and I'm not sure why. The clematis is grown in a container on my balcony and gets plenty of sun (the pot is protected from all but the earliest rays of the sun). I keep her nicely watered and have a few nasturtiums in the pot to shade her feet. Some of the lower leaves also have a bit of dusty black/brown "dirt" on them. Any suggestions from the experts? Thanks in advance! -bp!