Digital BW, The Print

hi. i'm pretty new to digital phtotgraphy and printing. i've recently 
set up a digital darkroom (nikon sc 4000, epson 1160, MIS FS quadtone 
inks). I'm printing portraits from tibet and the true black just does 
not blend in. the prints have a great tonal spectrum in the 
highlights and midtones, but when it comes to the shadows, the black 
blotches up and pixelates - looking very digital. am i doing 
something wrong? or is this just what i should expect with digital 
prints?
thanks so much,
dafna.