The 9th picture and teh 11th are small,but the rest are big. They are all configured to be big pictures. The size of the picture that I uploaded are the same : 700 X1200 .
I would like all pictures to be big
Images inside posts are displayed at the size you select/set when inserting the media in content. They also pass through Jetpacks’ Photon service – you may want to turn this off to check out if it has anything to do with the size difference.