Please make the full backup of your site as well as the Theme settings export and check the issue on the Storefront theme to detect if our theme causes the problem. Storefront is a free theme developed by Woocommerce.
Hello,
in the Comments on the Basel theme (on Themeforest), I read that the problem of stars not filling with color, is a problem reported by several people.
So it is almost certain that this is a problem with your theme.
Furthermore, I cannot test by changing the theme, because the website is publicly online, and the customer needs to quickly publish the e-commerce too.