We cant really judge a lot based on one image.
I looked at your original colour Bob, and assume that it has has NO sharpening applied, even when re-sized for here, or is that wrong?
Ive uploaded a mod1, with 30% sharpening applied, which would be a general starting point for a RAW image (I know this is not actually RAW); then further post processing in LR or PS would result in further sharpening for uploading, so mod2 tries to emulate that. Both are quite a bit sharper than the mono images.
So you have to think about sharpness as starting with the light; the lens ability to resolve fine detail (acutance); the sensor ability to record it; the post processing.
In general, its quite difficult to sharpen an image that is not intrinsically sharp enough to resolve at least medium detail. So you lens is likely not bad, but my not be great. The journey to a very dark and heavy mono, with layers of colour will all conspire to reduce apparent sharpness, unless close attention is paint to how each step impacts how the image looks in this respect.
I am attaching a Photozone performance test of your lens, at 16Mp, on a K body. It indicates its an extremely poor performer, to such an extent, they send the lens back to the manufacturer as they thought it was faulty; it was within specs. So to me, you are likely to be in extremely poor lens performance territory at f/14, and from the test, anything smaller than f/8. Try the les yourself at f/8 and see if it performs better.
So a mix of everything I think, suspect poor lens performance especially at this aperture; processing, and sharpening.
Hope this helps.