Responsive Gallery

Hi, I'm having trouble with getting the Jetpack Mosaic gallery to be responsive. I have to keep the mobile responsive setting within Jetpack turned off otherwise it overrides the theme and looks rubbish, but without it being turned on the gallery doesn't work on a mobile. I asked Jetpack what to do about it and they said it was something that needed to be sorted from the theme side - are you able to help? Thanks! thesalonmelton.co.uk/gallery