Thanks for the reply.
Please try to disable all the third-party plugins (including cache plugins), that do not come bundled with XStore https://xstore.helpscoutdocs.com/article/36-included-plugins , clear the cache of the browser, and check then. Maybe one of the additional plugins is the reason for the problem.
Or add the next code in Theme Options > Theme custom CSS
.single-product .et_product-block .woocommerce-product-details__short-description,
.single-product .et_product-block .product_meta {
font-size: 16px;
}
Regards