Special characters displaying smaller than the font size

Maybe this is the reason:

Google Fonts Diacritics
03/12/2018

Diacritics is a scripting type which is not supported by Google web fonts. Because of this, those letters will render as the fallback font and not in the font selected by the user. These characters may look like they’re bold, but in fact, that’s just the default style of Diacritics.
To solve this issue, please select a different font and see if the new font renders the diacritics in a better manner.
To learn more about this occurrence, please read this in-depth article.

https://jakearchibald.com/2014/minimising-font-downloads/

This solved my problem.

https://stackoverflow.com/questions/17922766/does-google-fonts-has-diacritic-diacritics

Many of them do, to find out wether they do or dont contain your characters go to https://www.google.com/fonts/ and find your font, open it by “Pop out” button and look for your characters. If the font contains characters you need, go back and click on “Quick-use” button – this will open the page where you can adjust some options and it will generate a code for your page – something like this:

<link href=’https://fonts.googleapis.com/css?family=Meie+Script&#8217; rel=’stylesheet’ type=’text/css’>

Now you have 2 options:

1) You dont care much about the page load – just add &subset=all to the href attribute and the link will load all the characters the font has. So you will have something like this:

<link href=’https://fonts.googleapis.com/css?family=Meie+Script&subset=all&#8217; rel=’stylesheet’ type=’text/css’>

2) However if you do care about the page load, you should load only character sets you need – on the google font page which generates the code to use – notice the “2. Choose the character sets you want:” section – there you can use (“Quick-use” page) choose which character sets you will be using and you will get something like

<link href=’https://fonts.googleapis.com/css?family=Meie+Script&subset=latin,latin-ext&#8217; rel=’stylesheet’ type=’text/css’>

Notice that now there is a list of character sets in the &subset attribute .

EDIT – IMPORTANT NOTE FOR LATIN-EXTENDED:
Fact that a font has latin-extended set does NOT mean it has all caron / ring letter-variants – especially “?” is oftentimes missing…

The problem comes back after a while. It can be solved again as described, but than it comes back.

Diacritics signs have displayed correctly after clearing browsing history from Chrome, Edge, Opera and Firefox. New version of my theme has overwritten style.css and header.php and the changes have been lost. I have not made the child theme.