Horizontal white lines through the text

the white ghost lines are down to the charge wire within the toner cartridge being dirty, the only real way forward is to replace the toner cartridge as access to the charge chorona wire is not possible without ruining the cartridge itself

A firmware update for your model addresses print quality issues. Please visit the Lexmark website to download and install the Lexmark Pro900 Series Firmware Update.
After successfully updating your printer, do a deep clean function. From the printer touchscreen panel, touch Ink Levels > More Options > Deep Clean Printhead. This will help clean the nozzles from possible clogs and dirt.
Then try to print a document again to verify that the problem is fixed.
If that doesn't help, please contact Lexmark Technical Support Center for further assistance.

22.6mm marks indicate a bad cartridge. Try a different cartridge if you have one.

Have you tried printing documents in other programs for example in "notepad" or "wordpad?
If the lines do not occur in either of those other progrrams, then the problem may not lie in your printer...

if it does happer, however, you might wanna consider getting a new printer? if much cheaper to get a new one than to get an old one fixed.

Check the waste recepticle under where the ink cartridges rest in the home position. Over time, ink sprayed into this cup during cleaning cycles builds up to form a small mountain of congealed ink. If this gets too high, it makes contact with the printhead and drags ink across all your prints. If there is a ***** of ink present, scoop it out with a spoon or a popsicle stick.

Dont get it on you, its messy...

you have a defective or near empty toner cartridge. Try shaking it side to side

Check for scratches on the drum surface. If you have ran a lot of copies on there, its a good time to get it serviced. It could be the cleaning blade on the drum as well.

Your post "...it prints very faint horizontal lines in color..." is indicative that indeed your color printheads are clogged and would need repetitive deep head cleaning. This is of course would require that you keep on cleaning until such time as the faint color lines have turned to legible print.

have you tried running the cleaning options? that may help. or is your black ink running low?

Sounds like a bad imaging drum to me...