Sony 50mm f1.8 lens vs Sony 28-70mm kit lens - Sharpness comparison on A6300

  50mm  f4

 28-70mm at 51mm f4.5

50mm was much sharper in above comparison, but in the following pictures of plants, the 28-70mm one was actually quite sharper.

 28-70mm at 50mm  f4.5

 50mm  f4.5