My Ricoh 3110 appears to be printing a little on the 'light' side. Occasionally looking slightly washed out. Please, no Star Wars jokes

Print quality is fine but changing Powerdriver settings makes little difference. In contrast, my 7100 prints the same graphics slightly darker.
I left both printers on whilst away for a fortnight. Had to do a head clean on both when I returned so it's something to do with this, both were printing identically before I went away.
Done the usual nozzle checks etc. just wondering if anyone's seen this before?