instructions for flushing one color

Can I flush just one color or do all the colors need to be flushed together? My Photo Black on an Epson 7890 is missing just three lines on the nozzle check print in the middle of the pattern. I’ve cleaned it several times, normal and power and I can’t get those three lines to appear. I bought a PK cartridge flush kit from Inkjetmall, can I just fill the cartridge with piezo flush replace just the photo black cartridge with it and run cleaning cycles?