Inject a bit of isopropyl alcohol directly in the port on the printhead and let it sit for 20 minutes. Run a cleaning cycle and do a test print. If it helps, but does not clear it, print an entire sheet with yellow. You can google "yellow printer target".
If you are still not getting a perfect result, repeat the alcohol cleaning, making sure to let it sit to dissolve the ink.
You have to have a bit of ingenuity to inject the cleaner. Use a hypodermic and small tube, or an anti-freeze tester or similar mechanism to pump in the alcohol. This usually works.