It is a great lens but in my experience, it is calibrated for medium and far distance out of the factory (at least the copy I have owned). In Sigma's term, the median distance is either 3m or 5m for this lens (I don't remember the exact as this was 5-6 years ago). My copy back-focuses a lot when taking pictures at a close distance. Looking at the photo you posted, it is obvious that you are taking the leaves at a close distance.
You don't need to send it back to Sigma for calibration and the focus calibration also has to do with the tolerance level of the camera you are using. You need a lens calibration tool like LensAlign mk II, a tripod, the Sigma USB dock, and lots of time.
The process is to set the alignment tool at close/medium/far distance, put the camera on the tripod, and take a picture of the alignment chart. You load it up on your computer and decide if it is back focus or front focus. You use Sigma USB dock software to adjust the focus adjustment per distance. The process is repeated so that you get pin-sharp focus directly out of the camera. Please make sure that any focus adjustment setting on the camera is turned off (I am sure 5Ds has this feature).
