Does the print have streaks on the image or is it just weak color? The thinking is the heads may be clogged but that would produce streaks. You can run a troubleshooting test with the Canon software that prints the color on a page. This would also tell you if one color was not working which may not produce streaks but would produce awful color.
To clean a head, remove the cartridge and use a clean Q-tip soaked with Alcohol and dab on the print head. Let it soak for a minute and then use a clean Kleenex tissue to lightly dab away the alcohol. Re-install the ink cartridge if it is good and has ink.
Ron