I have planted some MG's in some pots to climb a trelles. They are doing great but I noticed that some of the leaves at the bottom are turning completely yellow. Why? The pots have good drainage. I keep them watered. They get plenty of sunlight. They are growing like crazy. The pots also have petunias growing in them and they are doing great. I suspect they need fertilizer as the soil could get drained after several waterings. If they need fertilizer what kind should I apply? Any recomendations? I live in Maryland.