HP Office Jet Pro 6978 Print Quality

Hello,

I'm having a problem with my HP 6978 printer being unable to consistently utilize blue ink when printing color images.  I have run the Clean utility.  The samples print out perfectly, but my print jobs do not.  I have run over 16,000 pages, and have used only Instant Ink in the printer.  The issue seems to be exactly the same as what is described in this thread.  However, because the solution was moved to private messaging, I can't see how to solve it myself.  Any help with this would be appreciated.