Focal point looks to be Infront of the shell, as with Macro the DOF is very shallow….your focus point needs to be spot on.
Did you use a tripod and cable release, if no would recommend, will help you compose the shot and maintain your focus point.
Highlight on the right of the shell are slightly blown.
If you share your setting, you might get some More CC from the more experienced Macro Photographers on the site.