Changing “Leave a reply” text

Hi there!
I’m trying to change the “leave a reply” text, but I just can’t do it.
I installed the child theme for Customify, it was automaticly translated to Spanish, and it was all good, until now that I need to change the “Leave a reply” text (“Deja una respuesta” in Spanish) for another text (something equivalent to “Leave a comment”).
I looked into the files and I don’t even find the “leave a reply” text.
Does anyone know where do I have to look for it and how do I change that bit on the webpage?

The page I need help with: [log in to see the link]