Digital BW, The Print

Scanning, I print as much color as B&W and usually print B&W via QTR... 

I usually think of small prints (8X10) as proofs for 12X18 ...

Large color and QTR/B&W prints consistently look sharp from 35mm so
I've not paid much attention to small B&W print (proof) sharpness
until a new image that I want to print 8X10... 

Problem: This sharpness-demanding image (machinery with small details)
looks unsharp at 8.5X11 using QTR (sepia toned), but  distinctly sharp
using B-O. 

This seems not just contrast: unsharpness is obvious at edges of very
small type in the image as well as metal details.

I just ran a nozzel cleaning and nozzle check....everything looks perfect.

Question:.....Is QTR's use of multiple pigments inherently unsharp Vs
B-O's use of only two pigments?