Impossible to disable underline on title

Hello,

First of all thanks for adding me on this groupe

I've got a strange underline that comes only with titles h2, h3 and h4 (not heading 1), as you can see below.
This appeared since I've installed the Ally child theme for Divi.
I tried to modify theme settings, including using CSS Hero, but nothing does ...
I've noticed that Ally has a specific class named 'ally-lines' (witch generate lines on the right and left of a text. I'd like to see inside the CSS of this class but I d'ont know exactly where to find it, as I'm not experienced in coding.


Could someone help me to find a solution ?

Thanks in advance

Olivier