Usemin CSS only gathers one file

[PBartrina]

In mu usemin options files, it is declared as follows:

module.exports = {
    html: ['<%= paths.dist %>/*.html', '<%= paths.dist %>/components/**/*.html'],
    css: ['<%= paths.dist %>/**/*.css'],
    js: '<%= paths.dist %>/**/*.js',
    options: {
        assetsDirs: ['<%= paths.dist %>/**']
    }
};

Usemin does all previous processes perfectly, but when it comes to load files into the final html, it only detects one of them. The files are all inside the same folder, one next to the other.

Any clue?