Matthew,
First question, are you using Epson cartridges? If so, then I think you may not have the bottom of the print head clean enough. I use strips of paper towel cut, not torn, about 1 1/2 inches wide, folded in 1/3s to about 1/2 inch wide. I work them under the print head, put a few drops of Windex on the towel until wet but not dripping. I slide this back and forth pullling gently against the surface of the print head. I repeat this until they come out fairly clean, then repeat with dry strips a couple of times. print some nozzle checks and you should be good to go.
Also, while the print head is moved off the park position, use a long Q tip and Windex or distilled water to clean the o-ring on the capping station. Sometimes paper fibers and in my case kitty hair can keep it from sealing properly.
What often happens with matt type paper is fibers can come off the paper and stick in the ink spray, causing a buildup of fibers and evaporated ink. This has happened to me with both dye and pigment inks.
Hope this helps
Rich