Hi Harry
I've just been looking at the EXIF data for your landscape photo and I think the reason this shot isn't particularly sharp around the buildings might be your aperture.
You've shot this at
f/4.2 at 118mm focal length which is a pretty wide aperture for this sort of shot. Because you've shot in shutter priority mode, the camera has selected the aperture to get what it thinks is the best exposure but the DoF at
f/4.2, combined with the smaller DoF at longer focal lengths could well be the reason it's not particularly sharp.
Do you normally shoot your landscapes in shutter priority? If so, go back to the shots that aren't sharp enough and see what the aperture was on each shot.
I would recommend shooting in either aperture priority or manual mode and selecting an aperture of
f/11 or smaller (although Flake will be along before long to tell you all about diffraction and why you shouldn't use anything smaller than
f/8

).