Just a simple white balance Macro using a 50% gray and threshold layer.
- move the Threshold slider to this point where the first black dots pop up
- the marked Threshold slider is not working properly (mouse wheel and arrow keys dont work), to fix this use the mouse for 1% at the time
- mark one of the black dots, delete the 50% gray and Threshold Layer
- use the White Balance Picker on this spot (the picker uses only ONE pixel [sadly], so zoom in as far as you can)