F16 is probably contributing to softening your shots. Are you sure you need that much depth of field?
Viewing images at 100% (or whatever high magnification you're at) is making them look soft. Note that viewing a D7100 photo at 100% on your monitor at home or zoomed in to 100% on the rear LCD of the camera is equivalent to a five foot wide print viewed from a few feet away. Not very realistic or useful as a means of judging sharpness.
Post links to some of the photos which concern you. It would help to see what you're seeing.