Was it dry and crispy or limp. Yellow leaves are signs of over and underwatering but usually the crispy or curled edges are underwatering. MIne gets 5 minutes twice a week with some spray on just leaves from grass watering. Its about 2 feet above the grass.

It was dry and crispy, leaves turned from grey green to silvery grey. I'm thinking it was probably lack of water, so I went ahead and gave them some water yesterday. Thanks for the response!

Did you just plant them? They do need water to get established, and to look good, but not to survive, apparently, because I can't get rid of mine after years of trying. The roots go way down deep and they come back from the roots every year no matter how carefully I dig them out.

They are three years old, so I was experimenting with their first year of minimal watering. Another possible cause came to me, I have lost a lavender plant out there to repeated dog-pee attacks. It's possible the dogs who walk by decided that salvia was the new target, it is one of the ones bordering the edge of the bed.