I usually see purple on plants like lemon balm and such when they are stressed by temperatures (cold in my case). Extreme temperatures or weather there?

FataMorgana

whenever i pick my lemon balm (which is in the mint family), which is OFTEN to harvest it, the harvested leaves turn purple...could these be dying O_O?

I've never had harvested leaves turn purple. They dry green. I've only seen a dark color on harvested leaves (black!) when I tried to use a food dehydrator to dry them. The lowest setting is just too hot for it.

FataMorgana