Does anyone know what might be causing the leaves on some of the branches of this vine to turn a bit purple and wither? And recommendations on how to treat? My only treatment so far is a light spray with some neem oil this morning. This vine is a Kellog's Breakfast variety planted in a raised bed among several other varieties. So far this is the only vine affected and it's on 3 branches. I'm in central Alabama, Zone 8. Thanks for any guidance!