I have a new problem on my iPhone 6 where the battery drain has suddenly become a problem. I used to be able to pull the phone off its charger in the morning, go to work listening to my iPhone via BT Audio, read some SatGuys at lunch, and make it home with way over half (usually 65-70%) of the battery. Now, I can't make it through the afternoon without hitting the 20% warning, when I activate the battery saver. Unfortunately, this doesn't seem to help much.
So I dropped by the Apple Store and the Genius ran diagnostics on my iPhone. Everything came through with flying colors, no hardware issues found, and no wayward apps, either. So he reset the Firmware and after driving home, I'm almost done restoring the backup and all my Apps. Even with the secure backup, I still had to enter iCloud password, re-register my fingerprints, re-add my ?Pay cards, etc. Hopefully, this fixes it or I may have a replacement iPhone 6 and need to do this all over again.
I don't think it's an iOS 9 issue, but I have a fresh new copy of it to see if it makes any difference.