Why does my Climbing Susan Vine have yellow leaves?
I was fertilizing it regularly with 15-30-15 and kept it moist. In August the leaves began to turn yellow and it stopped flowering. I have since repotted it with new looser soil (because I read that the roots can bunch up and don't like being soggy) and stopped fertilizing. It is now flowering a bit but the leaves remain yellow.
Given your growing zone, I feel that the vine may be just beginning to wind down for the winter; in colder zones, this vine will be more of an annual and not likely to winter over.
The leaves also look like they are exhibiting the look of iron chlorosis.
You could save seeds from your plant to plant next season!