My Canon Pixma TS8050 has stopped printing any colours other than Magenta and PGBK black. I am using genuine Canon cartridges and have tried replacing a cartridge, but no effect. I have also run the Clean and Deep Clean routines multiple times, to no effect. I then removed and cleaned the print head, but it made no difference. Nozzle check pattern prints show a full grid of PGBK, then all the remaining codes (C to GY) in Magenta, with three full bars of Magenta and nothing at all against the other colours (C, Y, BK, GY). This happens whether printing from PC or using the printer's own onboard utility. Is there anything I can do? Printer is over two years old, so out of warranty.