They weren't sprayed by someone else where they? Either that, or once a week isn't enough... Mints are considered water hogs in my neck of the woods, not drought tolerant at all.

Yep, I'm with Heathen. I'd up my watering routine to every 3 days or so. Most of my mints are in pots, and I water every other when it's over 90 degrees.
The fence sounds like a good measure too.
Just whack them back, and start afresh.
Enjoy! Lynn

Mine have not done that and I never water them, good year or bad. someone may have sprayed or someone with a full bladder may have ????
I would probably chop them off and keep watering and see what happens. It is really tough stuff. The only thing I've found that they really really don't like is being lit on fire, and then they still come back (it just takes longer)

If it turns out you need more, contact me!

I have chocolate mint in a pot, it wilts when it needs water. My potted orange mint dried out, that's coming back now but is dried looking on the bottom half. I have unknown mint planted near a lilac bush where it doesn't get anywhere near enough sun, and the lilac sucks up all the water. I think that one's done for the year, but it will be back next year.

It is possible to kill mint, I bought a Kentucky Colonel mint this spring and forgot about it. It dried out, and even potting it up and watering well didn't bring it back :(