It would be helpful to see a nozzle test print and the edges of a fill test in service mode. Please post these to help in determining what is wrong. How old is the printer?
Your issue could be any of the following:
Needing a thorough ink system cleaning, i.e., caps, wipers, all around head area.
Encoder strip needs cleaning.
Dampers or print head starting to fail.
If you need a permanent solution you should go with Jim Hancock's list, If you need to print that particular sticker in a rush just go unidirectional, 100% k, slow speed/many steps. Also double check head height.
As Joe said, calibrations should certainly be part of the process to fix the issue. And as ewded suggested, check the head height. Fine text will print better on a low head height. My concern is when I zoom in, I also see some overspray around the letters. This could be head height, media static, cleaning or the printhead. Printing the fill test in service mode will tell a lot.
Press the panel buttons in the following sequence:
Main power on, front panel power off. Press the panel buttons in the following sequence:
Down, right, left, up, right, down, left, press and hold right, left, and down buttons all at once and turn on front power while holding those buttons down. You can let go of the buttons after a couple of seconds. This must be down fairly quickly. If you get an error message about service mode, try again. Once successful, when you press the menu key you should see menu and service menu as choices. Setup sheet, do a nozzle test print. Then press the menu key, right arrow into service menu, right arrow into print menu, down arrow to test pattern, right arrow into test pattern, down arrow to fill and press enter. Watch how it prints, noting how the passes look and look for gaps in the passes. During printing, also watch the edges on both side of each color band. The edge of each pass should line up with the previous pass. If the edges of a color is stepping back and forth while printing, the bidirectional is off in that color. Also the edges should be very clean and crisp. Look for any overspray or steaking on the edges. This test will give you a lot of feedback about the condition of each color channel. If you post pictures of the nozzle test print and pictures of the edges of the fill test, it will be very helpful for the people here help you determine what is wrong and what to do to fix the issue.