Question SP300(V) Printing Issues - Cyan Ink Starvation / Black Overspray

My SP300 started acting up lately. While printing 4" CMYK test squares, I noticed that the cyan square had light coverage and minor overspray and the black square had overspray. I shook each ink cartridge and discovered that the cyan was empty. After replacing the cyan ink cartridge (OEM inks used for life of the printer), I performed a manual clean of the heads, wipers, and cap tops. I decided to replace the cyan/black cap top and primed it with cleaning solution. After running a medium clean, I reprinted the 4" CMYK test squares, but there was no change from the originals. Wondering if there was air in the system, I ran a powerful clean. Then I printed a full 8" strip of cyan at standard quality, but again no change from original (print was consistent across all 8"). I then printed a full 4" strip of black, but no change from original (it almost seems like there is cyan overspray). Finally I printed a full 8" strip of cyan, but this time at high quality and the coverage got worse. My next thought would be dampers, but with the horror stories I've heard about damper replacement I just wanted to get some other opinions first. Just to note, magenta and yellow are printing great.

Thanks in advance!

 

Static has been a bit of a concern with the weather in western NY; humidity is at around 30%. But there is definitely something else up with the cyan (see the attached service mode "Fill Pattern.jpg"). Cyan is showing signs of ink starvation, which is especially apparent when printed at standard and high quality (see attached "CYAN_High Quality vs Standard vs High Speed.jpg") - left square was printed at high quality, the middle at standard quality, and the right at high speed. The high speed print has the least amount of overspray and best coverage.

Even with the misses in the standard black test print (see original post), the service mode black fill pattern is reasonable, with little overspray and the expected hue. That being said, when I then print the 4" black squares I'm getting significantly different results, with different hues, between high quality, standard quality, and high speed (see attached "BLACK_High Quality vs Standard vs High Speed.jpg") - the top square was printed at high quality, the middle at standard quality, and the bottom at high speed.

I have noticed that the printer is stopping multiple times during each job to fill the dampers or at least that's what I think it's doing (the display continues to read "Now Processing"). I ran a visual check on the dampers and nothing looks out of the ordinary; the black and cyan dampers are just as full as the magenta and yellow dampers, no visible leaking. Just to note, I had run two powerful cleans prior to this most recent set of test prints thinking there may have been air in the line.

Shot counts are as follows: Count 1 - 566113KShots, Count 2 -1194095KShots, Count 3 - 1934528KShots, Count 4 - 1451058KShots.

 

Why wouldn't the issue show up in the test print then?