ESS pictures open are dark on Ipad

Hello,
I have created some galleries on my site using Essential Grid. When viewing on an Ipad the pictures open up and are very dark. On my PC they look fine. I have looked for a setting to cure this with no success. I also checked my Samsung Note and when opening the same pictures from one of the Galleries, they also open very dark.

Also, what is the recommended image size for a gallery image. It seems to me my site is running slow.

Here’s my temporary site while I work on it: http://110.b16.myftpupload.com/

Thanks for your help.