Do you have the CISS or the refillable cartridges?
If the colors stop printing:
IF YOU HAVE A CISS:
It's likely that there's ink inside your air filters. Please check the air filters to make sure that there aren't any excess ink clogging up the yellow or magenta cartridges. This would cause the prints to start missing, stretch, or fade on the prints. The best way to clean these air filters is to throw them in a cup of hot water for 20 minutes. This should help the ink dissipate inside the air filters.
It's likely that the air vent plug needs to be removed. Make sure the air vent plug is removed, because this would be the same on the CISS if there is ink inside the air filter. IF the air vent plug is already removed, then there is possibly a clog inside the cartridge. If there is a clog, you will need to prime the cartridge from the nozzle and then perform a nozzle check to see if the prints are coming up to par. If not, I would repeat this and try performing a head cleaning after the prime, and then a nozzle check.
This nozzle prime is also applicable to the CISS system. If you have the CISS, you can also perform the nozzle prime. This may remove any pressure or clog that's preventing the cartridge from printing.
Here's a video showing you how to perform a nozzle prime. The printer model is different in the video, but it is the same maneuver for these types of cartridges with a nozzle on the bottom.https://www.youtube.com/watch?v=McHXJea9Xts