Hi Colin

I solved this by adding this script code in header part.

wp-content/plugins/jetpack/_inc/blocks/tiled-gallery/view.js?minify=false&ver=15.3.1″ id=”jetpack-block-tiled-gallery-js

• This reply was modified 7 months by viilevent.

Yes the problem is in the Retina, I think when creating the thumbnail itself not sharp.
I replaced the thumbnail manually, so it’s now sharp in the Retina and Website.
I think for now, that’s the only solution

Thanks a lot Calin

Yes I mentioned I have use that regenerate plugin
The problem is not the old image but the new one after I use this theme got this problem.

When I see the source code I notice that some use the image with 600X388 but the second photo using the original size image 900×600
That’s why I think look sharp

The other thumb size image being used in the big Grid but it’s sharp. Only in the block 5 have this issue, it use the 600×388 size but this size during generated it’s not sharp like others thumb

Thanks for your help. It’s working 🙂