Diviners Sage Humidity Problem?

I ordered three Salvia divinorum plants, two of which have died, and one is still alive and I have tried to increase humidity by putting a humidifier in the room, but the leaves are still turning brown from lack of humidity. I only have one plant left and want to make sure it doesn't die. Any care instructions would be appreciated.

You might do better by enclosing the plant in a clear plastic bag and closing the top, but leaving a very small hole open. Keep in bright light, but out of direct sun-light, since that could cook the plant.
Also make sure the water you use for irrigation is not too hard. Rain-water would be best and when you do fertilize use a very dilute solution. Over-fertilizing kills this plant.