Hi John, thank you for your reply.
Ok I think it’s not related to ACF because other plugins load their css files from main domain too :/
But it’s strange because I made a test with the default WP theme, ACF and only one other plugin.
Maybe it’s related to my Bedrock setup.
I found a temporary fix:
<FilesMatch ".(eot|ttf|otf|woff)">
Header set Access-Control-Allow-Origin "*"
</FilesMatch>