Lets start with a couple of general comments. I see your D7100 handles noise quite well at ISO 1600. That seems to give you good shutter speeds with ambient light and fast prime lenses. DX format cuts the angle of view, but a 35 mm lens is still a 35 mm lens and a 50 mm lens is still a 50 mm lens. There has been some discussion about suitability of 50 mm for portraits. There is even less support for using 35 mm as a portrait lens. The exceptions being environmental portraits where a good portion of the photo is background and your subject is well back from the camera. When I was your age, there was only film. The standard portrait lens was 135 mm because it flattened the face a little and made the nose less prominent. If you are sticking with prime lenses, on a crop body, 85 mm will give you about the same subject to camera distance as 135 on a full frame body, with similar framing.
Nesgran commented on sensor dust. Typically you will not see dust if you shoot wide open. If you stop down, then you see all the dirt! Like in this photo:
See the dot in the middle of your waterfall? Dust seems to get in when changing lenses. Then when shooting the mirror moving causes the air to swirl and the shutter opens to let floating stuff blow into the sensor area where a static charge may attract it to the sensor. The sensor itself is covered by a wafer containing several filters. The number varies by make and model, not all cameras have a low pass filter in the wafer.
I have never used compressed air and this site is not now recommending compressed air from a cartridge. I do use Eclipse fluid sometimes. When I got my 30D, I was plagued by sensor dirt. I think vacuuming out my camera bag was the biggest help! Still, sometimes I still have to clean the sensor. I use Eclipse fluid and special lint free wipes, called Pec Pads, wrapped around a kitchen spatula cut down to the height of my sensor, instead of the products shown at this page: http://www.luminous-landscape.com/essays/sensor-cleaning.shtml. See method 7D on this page: http://www.cambridgeincolour.com/tutorials/camera-sensor-cleaning.htm.
Arctic Butterfly (http://www.visibledust.com/products3.php?pid=3) has put more dust on my sensor than it ever removed. I don’t use it.