Clogging may happen when the ink inside the print head dries up and thus you may get the smudged printouts. To see if you have a clogged nozzle, you need to print a Print Quality Check Sheet; once it is confirmed that nozzle is really clogged, you must Clean The Heads On Your Brother Printer. Here are the proper guides letting you to clean-out the clogged printhead nozzles:
Use the menu on screen to start a cleaning cycle first
Open the entire top of the printer, doing this you will see the printhead moving back and forth
Next, unplug the printer when the printhead moves all the way to the left
Now, place a piece of blotting paper under the printhead
Remove the ink cartridges from the printer
Use a syringe to inject 4 millilitres of water into the nozzle
Return the print head to the right and put the cartridges back
Now, you can print the check sheet to ensure that printhead is cleaned from top-to-toe.