How do I improve sharpness of foliage and distant objects during video recording?

Lately I have tried recording some video using my old Canon. While I achieve decent results during macro shots and while filming human beings, I have noticed that foliage and distant objects in wide shots often lacks sharpness and are quite fuzzy/messy overall. Last couple of days I have filmed outdoors in strong sunlight implying ISO of 100-200, and while I have seemingly tried all possible combinations of shutter/aperture I can’t seem to be able to get crisp foliage and distant objects. Here I can note that I have not tried other focal length that 17mm yet, due to the fact that I want the nature shots to be wide.
After some testing I can conclude that it does not seem to be a problem of focus. I have not yet been able to conclude is the problem can be related to camera shake – however while placing the camera on a rail or table the results do not seem much better.

My setup is:

Canon 550D

Canon EFS 17-55mm 2.8 IS

Handheld/handheld while placed on natural surfaces

1920×1080 25 fps

AF during shoot: disabled

Movie exposure: manual

Links to sample footage displaying the problem:
(Imgur might slaughter the quality a bit, but it should be good enough as example)

Crisp flowers (55mm):

Washed-out foliage (17mm):

Is it possible to improve the results using my current setup? If not, what parameters should I look for in alternative equipment?

A final note is that I have tried photographing same foliage using same camera and while the result is better than video recording, the results are still somewhat fuzzy in comparison to shots of proximate objects on same focal length.