I hope this isn't a verbatim quote from the interview. Your interviewees were obviously very smart people, if they keep asking the same question (or what seems to be the same questions) it means you have not answered it properly. Therefore saying things like "As I already said" leaves an impression that you don't understand what they are asking.
Thanks for writing this up though. All too often we hear about the successful candidates. It's good to hear the other side of things.