I have a Prusa I3 that has been a workhorse for over a year. I've replaced almost everything on my printer except for the rubber belts. Recently I noticed that there are streaks on my prints where the filament doesn't come out as much as it should (see pictures). The printer is dialed in so it's not a level issue, I'm not sure what the problem is. I also noticed that my vertical layers have almost no strength which is something I haven't seen before. Has anyone had this happen to them or suggest the most likely cause? I was going to try the following:

1) Printing the same part in different configurations and locations to see if the problems happens in the same location every time. I usually print in the front left every time so it could be a wear issue. The lack of vertical strength makes me think maybe my filament has moisture in it or something.

2) Trying different filament

3) Changing the belts

4) Changing the feed wheel.

5) Replacing the power supply

Missing parts (unequal extrusion):

You can see the vertical spaces in this piece which has no strength:

Any suggestions appreciated, thanks in advance!