I am drying lemon balm for the first time and am using a dehydrator (I'm doing it at this very moment!). I've noticed within about 20 minutes of drying in the dehydrator, the leaves are turning black. In fact, the leaves were practically dried in about 30 minutes and are very dark (almost black). I only used the leaves with about a half inch of leaf steam. In the past I have dried parsley very successfully by hanging to dry. This is the first for using the dehydrator. Any suggestions about how to keep herbs from turning dark and black when I use the dehydrator? Is there a way to keep them and other herbs green (or their normal color) when drying in the dehydrator? Thanks!