Has anyone noticed that their 24-70mm is soft at 70mm? I bring this up because I noticed that my GF's 35-70mm is sharper @ 70mm than my 24-70mm both at f/2.8. I had the lens repaired in March but only noticed this recently. I will have another 24-70mm to compare in a week. Until then, anyone have experience with these 2 lenses?