I have 3 hanging baskets, spearmint, lemon balm, & peppermint. I've noticed the edges of the leaves, especially on the lemon balm, look like they have been scorched. Why is that? Is something wrong? Can I do anything to fix it? I really don't want to lose my herbs. The marks are even starting on the edges of the new little leaves. The picture is of a lemon balm leaf, but it is dark outside. I can try to get better pictures in the am. Please help!