I'm brand spanking new to the forum (and almost as new to gardening).

I have two mint plants (spearmint and peppermint) which have white spots on them. Someone told me that it might be mildew so I sprayed a mixture of water and baking soda. I did this yesterday. I checked my plants this morning and they are turning black and seemingly dying. Did I put too much baking soda? Are there bugs on my plants killing it? Can I save them? Do I chuck them and the pots?

I looked through the forums but I didn't get conclusive results.

I have more pictures if needed.