I don't know about anyone else, but the image doesn't help me much. Enlarging it just makes it blurrier.

How about a detailed description if an improved picture isn't possible?

what she said.. but also.. do you see anything on the back ??? ... though you would not see spider mites ...

something is sucking the life juices out of it ...

might be time to simply cut them to the ground ... and plan for next year ....

ken

Looks like a serious case of downy mildew and some cobweb situation....spider mites or regular spiders, I have no clue.

I'd cut them down to the ground like Ken suggested. Depending on where you are, if it's warm enough -- it might just grow back before the winter....
Or, if it were my plant, I'm more likely to pull them out. Mint is too common to come by or to grow from a simple grocery store cutting to have to raise this one again come spring.

Rhizo - is this any better for you?