Several photographers are having a hard time achieving an image that is perfectly focused when using the macro lens compared to other lenses. There are several reasons why this is usually the case.
When trying to capture an image at a short distance, the shake in the camera has a substantial effect on the result of the image compared to longer distances. Since you are very close to the subject, a small movement alters what is in the viewfinder of the camera far more than if you are capturing something that is far away.
If you try to hold your hand at an arm’s length and slowly move it and do this same motion right in your eyes, you can see the same effect. This same effect happens if you have your camera placed on a tripod and the subject you are trying to capture moves. This is usually the case when you are taking a macro shot at plants or flowers.
Animals and wind can cause these subjects to slightly sway making it much harder to get a crisp and sharp image. The shutter speed of your camera may also be relatively slow for the type of condition that you are capturing. A macro lens focuses on a very close range. It could be that you are focusing on the wrong part of your subject. Try to determine if any area in your captured image is focused sharply. This will aid you in checking the necessary adjustments that you need before finally making another shot.