Suggestions on cleaning up print

I’ve had my Taz 5 for 2 yrs now. I just noticed the print quality deteriorated a little. Any suggestions? The 2 parts are left and right, 2 different files and printed ~4" away from each other on the print bed at different times. The dirty parts of the print appear to be at the same area of the parts.
I’m using Cura.

Any suggestions?

When a 3d printer starts a new layer, it can start the layer either on the inside and do the perimiter last, or on the outside first and fill in. When it starts on the outside (which for some stupid reason is the default on most slic3r setups) it leaves a slight mark where the nozzle starts extruding. You can also tell the printer to always try and start at about the same position on the layer, which makes kind of a zipper looking seam, or you can tell it to randomize the starting point. It looks like you have it set to randomize the starting opint, but print the exterior perimiter first. For a smoother outer layer you want to do the perimiter last instead.