Print a couple of words in the biggest font in bold with huge letters in all 4 colours , black, yellow, magenta and cyan(or use the colour that you know is partially blocked). Print this on normal paper but in best photo mode. This will clean and purge the heads. The other advantage is that the ink is not ending up on the soak pad in the printer. I normally use this method for the colour that needs unblocking and safes me going through a full cleaning cycle.