I voted "Some of my lenses needed fine tuning", but if only it is as simple as that! The last thing I want to be is controversial, but this was my experience.
I only tried fine tuning out of interest, now I leave well alone. I have not tested any lenses on my D7100, so what I say here concerns my D800 only.
Firstly, I see no satisfactory conclusions can be arrived at tuning any zoom lenses unless it is to always be used at a specific focal length, thus treating it as a prime. There surely can't be "one size fits all" Why, because when I fine tuned my 70-200mm f2.8 it told me (FocusTune) +5 at 70mm and +15 at 200mm! My 24-70mm f2.8 returned -3 @24mm and +10 @ 70mm! In the end I did for a while set an average between the two readings. I noticed no real extra sharpness so returned all lenses to zero.
Secondly, my primes were all tested (50mm f1.8G, 300mm f4, Sigma 105mm macro OS) and the only lens outside a zero result was the 50mm which was +5, I left it alone. I had many other lenses which I didn't test.
My D800 and D7100 are providing super sharp results across all ranges and at all zoom focal lengths, so all my fine tune setting are at zero.
I am not for one minute doubting that there are those who have derived great benefits from fine tuning and of course many have. However, I used almost laboratory conditions and followed all instructions fully and found no benefits. Perhaps I should visit an optician