Sedum kamchaticum is a tough plant, and extreamly drought tollerant. Watering shouldn't hurt the plant if the soil is bone dry. The biggest problem I have with my sedum is ants. They love to create nests and will cause the plant to die. Check the area, and if there are no ants than only water if the soil is dry. Also, make sure nobody has sprayed herbicide near the plant. Herbicides can drift from 100 feet on a mildly windy day.

I wonder if maybe you are overwatering? Are you checking the soil before you water? I have a large swath of this on a dry rocky slope near the street, in hot full sun with the reflected heat from the asphalt, and I hardly ever water them.

Is this a new planting for you? I'd check that they are firmly planted, and then check the soil before watering. Hopefully they will spring back for you. This is a tough plant and hard to kill.

Good luck!
:)
Dee