Hi there. The Printer Doctor is in and ready to help you! If there is sufficient ink in the tank, you likely have clogged printheads in the black nozzles. Try running a printhead cleaning function as directed on the printer itself via the control panel on the printer. Run it a few times. If no improvement, try a new black cartridge. If you have the same problem with a different new cart, then the nozzles in the printhead for black have clogged to the point you will need to have an authorized Brother service center clean or install a new printhead.
Yes, I installed a new black cartridge and ran two tests, but no improvement.
I have just tried another test run, but to no avail. I will take your advice and take the printer to Best Buy and ask the Geek Squad to investigate. Thanks for your assistance.