My guess is that it is probably a fluke and that it won't happen again. When something like that happens, I usually suspect some sort of abnormal abuse, like maybe getting hit with a chemical like 2-4-D or something that sort of temporarlily maimed it, without killing it. On other plants 2-4-D will sometimes cause leaves to be distorted, or variegated in color for the one season anyway, without actually browning them out. I had a very distorted bloom stem on one of my irises but the other bloom stalk coming off of the same 'mother' rhizome was just fine. I wonder if I might have accidentally disturbed the roots on the one side or something at just the 'wrong' time to cause that to happen.

I suspect they will be just fine next season. Possibly others will have other opinions though. I'm fairly new to irises compared to a lot of the members here.

Sue