Repairing Mold and Discoloration in Photoshop Elements

Switch to the spot healing tool and soft brush of about 40 pixels. The options bar should be set to Type: Proximity match. Now use very small stroke, or even just a tap of the mouse button (or pen, if you're using a graphics tablet) over any areas where you see splotchy color variations. Keep going until the splotchiness is reduced as much as possible.

I find the spot healing tool works best when the brush size barely covers the area you are healing. Also, sometime the spot healing tool will introduce a new flaw, but a second click will remove it. If it doesn't, two undos will get you back to where you started and then you can try a different brush size. Below you can see how my image looks after working with the lighten brush and then the spot healing tool.