Hey there,

I am really sorry for the delay of this reply as it is a weekend for us here.

It seems like somewhere on your site already make those h1,h2,h3 font-size to be bigger, you can check my attached screenshot below.

I did applied this following custom css from your current template custom css section, it should show smaller size now.

body #eb.eb-view-entry .eb-entry-head .eb-entry-title {

	font-size: 25px;

}

Do take note, since you have using JCH optimise plugin, you have to disable this plugin first then only test modify the custom css, because this JCH optimise plugin will compressed your site CSS mean whatever you add the custom css code on your site, it will not get effected because your newest custom css haven't compress into this JCH optmise cache css file yet.