#1 Nice portrait, subject nicely seperated from background, clearly deep in thought.
#2 Boring, sorry. Might be of interest to someone with a fetish for wheels though.
#3 Needs straightening, unless the lake really does slope downhill
. I like the shot but I find the white huts on the jetty very distracting. The white draws the eye but then the object one is drawn to is obscured by the branches. I would have moved around a bit to find a better viewpoint, whilst still keeping the branches framing the shot. Slightly to the left would have enabled the huts to be a part of the scene, with the overhanging branches then falling to the right of them. It would also put the chalet in the background a bit more to the left and remove the other white building largely obscured by trees. At the moment the eye is drawn to too many objects and finding them obscured when focused on. The chalet and (unobscured) boat huts would make a nice scene.
#4 Very nice, I'm not a huge fan of HDR because people usually go too far with it, this one works well.
#5 Looks slightly soft to me, I suspect the focus is slightly too near to the camera (the nearer leaves look a little sharper than the flower heads). I don't know how much you have sharpened this image already, but a touch of selective sharpening on the flower heads may help. I would also crop it tighter and remove some empty space, but that's a personal thing. A bit off the top and the left would decentralize the flower and have it leaning into the image, leaving the open space on the right would then be fine.
#6 Again a little soft although the focus point is around the right area. Needs to be pin sharp on the butterfly head and with enough depth of field to cover (at least most of) the butterfly.
I'm not too sure why #5 and #6 are soft, as they don't look sharp even on the focus point. Things you might try thinking about are:
Are you sharpening in post processing, also resizing for the web generally softens an image and a bit of sharpening is required to bring back the 'pop'.
Are you using a tripod, or enough shutter speed to cut out camera shake. Equally, if using a slow shutter speed on a tripod, the subject may move slightly in the wind and cause a little motion blur / softness.
Try using a smaller aperture (larger number) to increase the depth of field, but don't sacrifice shutter speed too much in these situations. You may need to boost ISO to get sufficient speed and aperture.
Hope this helps a bit.