diacritics not displayed after cPanel migration

Hello,

I migrated a two sites from cPanel and the CWP running on RHEL 6.8. Everything when fine, but now I discovered that the diacritics characters are not displayed.
Do you have any suggestion how to fix this problem. Or at least which component is responsable for this?
One of the webpages is Wordpress, the other is Magento.

Thank you!

Istvan