I planted a heliotrope in Kellog Gardens Organic Plus raised bed and potting mix a month ago. Many older leaves have black spots on them or a black stripe in the middle, dry and brittle. It is on several stems but there are some stems that it has not impacted yet. There is good new growth coming out of the bottom. I haven't had my heliotropes do this before and I'm wondering if you have an opinion about it because I can't find anything online. Thank you, Linda