What version of photoshop elements are you using?
How are you rotating the photos?
I am using Photoshop Elements 10. I have scanned old large negatives from the 30s and Inverted them to positives. To rotate the image I was going into Image/Rotate. To tick the box for Constrain Proportions I went into Image/Resize/Image Size. They are all over the place for size, so I thought I'd maintain the proportions on rotation and then crop to a standard 4x6 before ordering prints. And thank you for being helpful. Sincerely.
After you rotate the photo, if you go to Image>Resize>Reveal All does that make a difference?