My wife and I planted 3 Bower Vines in our backyard and up until now they have been great. They have grown well, are flowering and get the full sun that is recommended. Recently the leaves have started to turn from a glossy green to a pale yellow color and they vines look a bit sickly. Any thoughts on what could be wrong?

Have you been getting lots of rain? A lot of the time yellowing of leaves occurs because of too much water.