I trim my original WAAAy back often as they get wild and weedy/The double is much more controlled. I have had a branch here and there die but not the entire bush
I THINK they are still under investigation as to how well they do for how long(in our climate) I just saw they have one at the research lab garden.The gardener said they are seeing how it does here.
Remember too all things have a life span. I figure plants to be like people.Some may make it to be octogenarians and some won't make it out of the nursery alive.
Sad but true.
tanya

Post a picture and we might be able to help more. Are the leaves crispy brown? Have they been getting too much water or not enough? Did you over fertilize?

I have 10 KOs, 5 pink and 5 red, singles... I got them abt. 10 years ago, on Fortuniana, and the only trouble I have ever had is the chili thrips love the pink ones... I feed mine well, organic, and have not sprayed for almost a year now, since I gave up granular ferts., but keep lots of organics on them and my other roses..... they get water abt. twice a week unless it rains.... very trouble free and constantly in bloom, I have to keep cutting them back down when I dead-head.... sally

I don't have any knockouts but my antique roses are not doing well at all right now and they're all types which are supposed to do well in the heat. I know the Cecile Brunner (Sweetheart) normally does well in the heat because we used to grow huge ones in SE Texas. It's the healthiest of the lot but not growing like I'd expect.

Really think this rosebush is doomed. Seems like right now only one branch looks good. My pink one right next to it is doing fine.

You know Knockout is on face book. They may help you if you friend them
tanya

Whoopee!!

Today I spotted a shoot in bloom nest to the original. Seems like the original cloned itself as I have a new Knockout right next to the one that died.