If you are using the default settings, you have to just override the h3 CSS style. From your site maybe. it is overriding the plugin h3 style. you can just decrease the font size from your WordPress dashboard Appearance>Theme Editor>style.css
putting this code,
.w3eden .card h3 {
font-size: 14pt !important;
}
it will back to you plugin default h3 style.
Thanks.
