I have a peppermint plant that a friend bought for me already potted at a farmer's market. I've been keeping it barely alive for the last 4 months. Its leaves turn brown and dye, then the brown deadness creeps along the stalk until I have to cut back the whole stalk. Then it will recover for a month or so and seem to be fine. But now it's back to dying off again. What is this? Some sore of fungus? I don't know what to do. It was out on my porch for a while before it got sick, then I moved it under the eve and it seemed to improve, but now it's half dead and the only live part has leaned out away from the eve, so I moved it back out into the open. I'm really not sure what to do with this plant. And since the brown disease seems to spread, I'm hesitant to eat the leaves. Help me please. All the information I can find online tells me that mint is hardy and needs almost no maintenance. I can't find anything on what's wrong with it.