what's the white dust on my herbs?

[basilosaurus]

I'm completely gardening challenged, but I've kept my herbs alive for a month. Now there's a white dust on the mint and rosemary, and I have no idea what it is or if it's something I should be concerned about.

Is this something in the soil that the plants are getting rid of? Is it from the general dustiness of my balcony, even though the basil doesn't show it? Is it from the salt air exposure (I'm 2 blocks from the ocean)?

Basically, will it kill me Thanks!

[basilosaurus]

Hmmm. These are outdoor plants, but it's so humid where I live that I'm guessing mildew isn't out of the question. It is certainly powdery, although the mint and rosemary aren't close together. I would have expected it to spread to other closer plants first if that was the case. I'll try a fungicide and see what happens.

[dirtyred]

If you use a fungicide, you won't be able to eat the plants.

I'd pitch and buy new.