Digital BW, The Print

Here's my set-up: Epson 1280 dedicated to MIS EB6 ink set for B&W
                  Not using QTR, just printer setting.
                  
Results have been quite good but print tones vary, mostly with a
change of papers. That is understandable.  What I don't understand is
I tried printing on Ilford Gold Fiber Silk and really like the dark
brownish rich tones of the paper.  I printed 3 different photos all
with the same settings resulting in the desired tone.  A fourth print
(different photo) was nowhere close to the tone of the other three
photos.  With everything being the same as the first 3 prints, why isn't the 4th print very similar to the other?  Can someone please enlighten me?  Thanks.
Tom