Yellow leaves could be a sign of too much water, or of root disturbance from a rodent, or from an insect or disease problem. Perhaps if you sent a photo I could make a better guess. I suggest you poke your finger into the soil and see if it is wet. Poor drainage may be keeping the roots too damp. This is the end of summer however and your vine might just be responding to the shorter days and starting to go dormant. The fact that it bloomed and grew this summer means it must like the location so I do not think lack of sun is the problem. Keep growing, Marianne Binetti