Horizontal Swiping a bit laggy

Greetings, i have an issue with the horizontal swiping of our magazine..

It is not too serious just that when we swipe it can be a bit laggy at times, as if its battling to load the next vertical. however the lag is very subtle not too noticeable, but one gets the feeling it is processing a bit slow..

Is this because our images are high res png? or is there something we can do to fix? 

please note none of our images have pinch and zoom enabled..

thanks alot