Okay, add a Levels layer on each photo, and move the Output sliders on each one. (Remember, the Output sliders are the ones under the gradient, NOT the ones under the histogram.)
First photo:
R 0/240
G 0/244
B 0/251
Second photo:
R 0/249
G 0/246
B 0/248
Third photo:
R 0/236
G 0/238
B 0/241