Digital BW, The Print

Using MIS hexatone VM inks with a CFS, I am have ab over spray on 
either side of the nozzle for the "yellow" (lightest gray) position 
output. A purging test pattern has an gentle plume of overspray all 
theway down the light gray test bar.

Is this correctable with cleaning? If not what is the next best 
solution? Replace the print head?

I need this for my black and white output for a high school course I 
am teaching. Any help would be appreciated!

Murray