Powdery Mildew on Mints

My lemon mint and wintergreen mints have these white spots on them. I have been told it was powdery mildew. I have used a fungicide for the past month, but it has not helped. I have also trimmed them down. Any suggestions of what this might be or what I can use for it? They are still growing vigorously, except for the above problem.

Powdery mildew looks like somebody dropped talcum powder on the plant and the plant portion affected by it dies off. Fungicides will not affect it unless they have a spreader sticker added to them, because the fungus has a waxy covering that just makes liquids sheet off it. What you need is a dishwash detergent solution that you turn the plants upside down into, swish them around a bit, rinse with clean water and repeat once a day until the problem seems gone. The soap dissolves the waxy covering of the fungus and the fungus dries out and dies. Just make sure the plant tops stay dry between treatments.
The beauty of this treatment is that it is not a bit toxic to you!