gallery thumbnails not showing up IOS and android

Ok – I have a gallery with thumbnails – all works fine in major browsers but when I check the site on an ipad/iphone/smartphone, the thumbnails seem to go monochrome(ish) and not very clear. If I put my images into the image folder in my theme and change the address to absolute then there are no problems but when the address is in the uploads folder the problems start.

This is a bespoke them with no plugins (apart from Advanced Custom Fields). Not sure if that plugin is causing the problem??

Can anyone shed any light? Thanks in advance.

address: www[dot]lucyanne[dot]co