Line Width Too Thin.

Recently, I have noticed that the lines on prints are too thin and not sticking to each other, resulting in weak parts. The infill does not stick to the wall either.

I have tried different settings and done about ~15 test prints, with no success.

Does anyone know how to solve this problem? Any help would be greatly appreciated.

(If you would like to see a picture of the test prints just ask)

Maybe your nozzle is partially clogged?

I just replaced the nozzle, so I doubt this is the problem, but I'll clean the nozzle anyways.

Were you able to solve this issue? I'm having the same problem and have tried countless variations with slic3R.

I had a slightly similar issue. Measured the filament and found it was 1.7mm instead of 1.75. Set the flow multiplier on the printer to 105% and the problem is gone.
The correct fix is to change the filament size in the slicer but this is a good way to get a quick confirmation by reprinting an item with the same Gcode.
Filament size can vary over the length so recheck when problems occur.
Note, the area is a function of the square of the diameter (Pi x Rsquared) so small changes have a significant effect.