may be diminish the compression level when you export as there is a big difference in size between your 2 images (the original image is ~190 Kb, the darker image is ~150 Kb)
Other than that, the only thing which comes to my mind right now is the color profile, you might have some clipped colors at export
did you tried to save the color profile while exporting?
Other than that, the only thing which comes to my mind right now is the color profile, you might have some clipped colors at export
did you tried to save the color profile while exporting?