Welcome Dave. You seem to have taken to street photography like a natural. Good taste in cameras also! Something I've learned with the GRD IV is that the snap distances can be a bit misleading. You would think if it was set to 2m and the lens was wide open then you better snap your subject about 2m away. I shot just such a subject today at F2.2 and 2m snap and the couple I shot were a little soft yet the scenery in front was tack sharp. I guess there may be variation from camera to camera but perhaps you should shoot wide open for a bit and check the accuracy of the snap distances. If you stop down to F4 and beyond then chances are you will get everything reasonably sharp so long as your shutter speed is high enough.
Also test your image stabilisation. Mine stopped working after updating the firmware.