At such a low angle and narrow DOF It's hard for me to tell exactly where it is sharpest. At 2 feet from the subject, f/2.8 at that focal length you DOF is less than 1/2"

When I look at your un-cropped image in Photoshop where I can review it larger, I can also see the center is just left of(behind) the eye. On my monitor the side of the frogs head does look to be in sharpest focus. The green leaves to the left also look to be sharp probably because they are in line at the same distance as the side of the frogs head where you focused. Because of their shape and color the leaves will be more noticeably focused.


Did you open your image in DPP and view the focus points to confirm where your focus point hit.


To calculate the DOF you can use this web site.


www.dofmaster.com/dofjs.html