Gallery images not showing up

Haven’t been editing the site this week, but at some point some of the images for the gallery here disappeared: http://karolle.com/exploring-low-cost-private-schools-in-hyderabad/

I’ve tried removing and re-adding each one, but no luck. Funny thing is, one set of images are always missing in Chrome, and a different set always missing when viewing in Safari.

Anyone else experienced this before? Might it be my browser / wi-fi not loading galleries properly?