Printer can copy, but does not print

Hi

I have an Epson Stylus BX600FW. Recently I changed printer cartridges. Since then, the quality of my print outs is very bad, as if cartridges were out of ink. OK: bad printer cartridges, I thought. Instead I printed the typical Windows sample sheet and I even used the printer as a copy machine and the quality of the results was excellent.

Because of that I thought something is wrong with the printer set up, but cannot figure out what. (I did not change or touch anything, tough. And the printer was working before)

I cleaned nozzles and printer heads hundreds of times: no improvement..

I printed from 2 different computers (Windows): same results

Thank you in advance for any advice you may give...