Laravel 8 + Tailwind PurgeCSS

I'm trying to deploy an app. I am using mix as configured out of the box.

When I run npm run production

I expect that the app.css file to be purged of extra tailwind classes, but the resulting file is 4.5MB

My webpack.mix.js file looks like:

const mix = require('laravel-mix');

/*
 |--------------------------------------------------------------------------
 | Mix Asset Management
 |--------------------------------------------------------------------------
 |
 | Mix provides a clean, fluent API for defining some Webpack build steps
 | for your Laravel applications. By default, we are compiling the CSS
 | file for the application as well as bundling up all the JS files.
 |
 */

mix.js('resources/js/app.js', 'public/js').postCss('resources/css/app.css', 'public/css', [
    require('postcss-import'),
    require('tailwindcss'),
    require('autoprefixer'),
]);

mix.copy('resources/img', 'public/img');

My tailwind.config.js file looks like:

const defaultTheme = require('tailwindcss/defaultTheme');
const colors = require('tailwindcss/colors');

module.exports = {
    purge: {
        content: [
            './storage/framework/views/*.php',
            './resources/views/**/*.blade.php'
        ]
    },
    theme: {
        extend: {
            fontFamily: {
                sans: ['Nunito', ...defaultTheme.fontFamily.sans],
            },
            colors: {
                lime: colors.lime,
                orange: colors.orange
            }
        },
    },

    variants: {
        extend: {
            opacity: ['disabled'],
        },
    },

    plugins: [require('@tailwindcss/forms')],
};

Am I missing something? The app is not very big or complex, so I know I'm not using all 4.5mb of tailwind.