My impatiens are not doing well this year. I planted them from 6packs in early May, and they're not much bigger than they were. (This is the same area I planted them last year...under a persimmon tree.) I added a slow release fertilizer and the soil savers in the planting hole, hit them with some root stimulator at the time of planting, and have hit them with Superbloom twice since then. They get watered when the lawn gets watered (about 1/week) + the two extra fertilizer times. They don't seem to be growing. Any thoughts?