Unite gallery images blurry?

The images on https://wangjingwei.org/ were done in Unite gallery Tile justifed, but they are blurry on Android tablet and iphone, but look good on Imac and ipad. Is this something I can do in settings? I have now tile resolutions set to “full”, would changing this make a difference? I also started replacing images with larger ones (in size), but it seems to have no effect. Any advice or suggestions would be appreciated?

Thanks,