Clogged printheads are the main culprit to consider when ink is not printing out onto the paper (either not at all, or streaks). In epson inkjets, the print heads are in the printer, so the issue is likely not with the cartridges, but with residual ink lying on the print heads that has clogged. This can happen due to non-use for a period of time, or due to mixing different inks through the same printer. Epson is aware of this problem, so they have a print head cleaning cycle in all the Epson inkjet printers. To run a print head cleaning cycle on your epson printer, look up the function "print head cleaning" in your manual, or through the menu options on your printer. This is usually an option in maintenance, right along side the print nozzle check function. Some printers also have a deep cleaning function. Cleaning the heads once or twice should resolve minor clog issues, and to keep the ink flowing through your printer you should print a page or two a week.