I have several potted climbing roses in my urban garden. They're planted in
large half barrels. They've done very well for about the past 3 years. This
year, the leaves are smaller, duller, more sparse and a few canes died. One
potted shrub rose that I had for 5 years, died completely. I feed them as
I've always done (twice a month), water as usual. What's going on?

Thanks.