Switched to Auto rather than portrait, slightly overcast today. Still not sure if I'm using the polarizing filter correctly, but much, much sharper!

Here is a link that might be useful: Magnolias2

In some of your photos, the camera has focused on a background feature instead of the main subject, for example, the brick wall and the woven fence. In these cases, you may have to resort to manual focus.

The auto-focus technology is not perfect. It follows a set of its own rules and these do not cover all situations. In one case that I know about, the focusing routine (algorithm) looks for hard edges in the scene and adjust the lense to make these as sharp as possible. Thus, the focus routine fails if the central subject is fuzzy. It has difficulty in focusing on fuzzy thistle blossom, but may settle on the leaf edges seen in the near background.

I have another brand of digital camera ( a much earlier example). This had excellent color renidition, but only 2 Megapixel. This one had a particular focuing rule: If it could not find a suitable edge to focus on, it racked the lens to infinity and led one to believe focus had been achieved. This was done to keep the focus mechanism from hunting when the camera was aimed at the sky and or clouds.

Many of your macro shots are lovely, but then an occasional blossom is out of focus or poorly exposed, or does not have enough dynamic range to differentiate between the varying shades of white. Some of the blur may be due to motion of either the camera or the subject, but I did not detect the unidirectional smear typical of a wind blown blossom.

There is a need to increase the depth of field for closeups of the blossoms. This is done by using a small arperature. For floral photography, you can shoot as slow as 1/30 sec with a tripod (highly recommended). Also, a larger len opening, say f/ 5.8, can be used to narrow the plane of focus.

You have a Canon Powershot A630. I have the Canon Powershot S2 IS. There may be some similarity between these models. I was disapointed with mine until after I made a series of test shots. What I discovered was that the dynamic range of the sensor was not as large as I expected and the white to light colored objects were burning out in scenes with significant dark values. The default setting was overexposing a bit. This was corrected by reducing the exposure by 1/3 f-stop. (In my camera, this is not adjustable in the auto mode. Switch to the P (program) mode to make custom adjustments.) The default sensitivity is ASA 80. This results in slow shutter speeds for reduced light. This can be boosted to ASA 100 without much noise effect. In fact, the gain in shutter speed will more than offset any noise increase.

With these adjustments, my shots were much improved. In a few cases when the result is too dark, it can be brightened with processing software. However, if a scene contains a burned out image, no amount of processing can save the picture.