Digital BW, The Print

I'm sure this is another naive, ignorant question, but possibly due to using
different paper settings today, I've got a noticible change in image tone.
These are all b&w prints coming from my 4880 using K3 inks. Today's print
has a metalic brown, olive green hue in the highlights when viewed from an
angle whereas yesterday's is pure black from all angles.

So, what caused this change & how do I avoid it?


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