I purchased this razzleberry plant 3 years ago through Better Homes and Gardens magazine. It always bushes out well on top but it never produces any more than one tiny cluster of berries of which only one berry ripens. As soon as the plant matures in Spring, the bottom leaves inside the pot start to turn yellow then brown and crispy and die. The whole while the canopy stays green and full and several volunteer plants begin popping up with the same issue. What could be wrong? Soil?