Watermark images are not updating
If you change the watermark after you have uploaded images, all the previously uploaded images will not be automatically updated. However, you can update them very easily using a 3rd party plugin like Force Regenerate Thumbnails.
Update your watermark
Install the Force Regenerate Thumbnails plugin
Go to Tools > Regenerate and run the process. It might take a little while if you have a lot of images.
This is required because watermark images are not dynamically added to each image as the page loads, instead they are permanently added to the image from the original and saved to your server. Regenerating the images will recreate the proper image sizes Sunshine needs and apply the new watermark at the same time.