The problem is that;
in the single product page,
your product image is resized to fit a larger area than the original image size.
Speaking of this sample product (Hot Tamali)
your original image size = 188x218
in category view it is used as: 175x203
in the single product page
the product image is : 137x160
but resized to : 200x234
to fit that thumbnail area,
because of the
In the WooCommerce Settings,
there is a section to control the product image/thumbnail sizes:
WooCommerce > Settings > Catalog > Image Options
You can redefine your image sizes and as it is described there, in order to take effect, you have to regenarate the new thumbnails using a plugin.
BUT; again, if you use smaller images than the area, it will try to resize it to fit the area. Resizing a bigger image to a small place won't disturb much but enlarging will make the images look blurry/pixelate.
After changing image sizes and regenarating the new thumbnails, you may want to change that css rule as
and it will not try to fit the area...