wasn't totally sure where i should post this, but here goes anyway. i have about 7 morning glory vines growing right now. they're quite large and nearing flowering. i was wondering if the bottom leaves are sposed to be falling off, they're already quite yellow. i had pretreated the soil last year for nutrients so they shouldn't be lacking. i'm only worried cause about 2 1/2 feet of each plant are full of yellow leaves.