You could also wrap them in a group:
Route::domain('payments.example.com')->group(function () {
Route::get('/', function () { return 'welcome'; });
Route::get('payment/{id}', 'paymentController@paymentHome');
Route::post('paymentStripe', 'paymentController@make_payment');
Route::get('paymentFails', 'paymentController@paymentFails');
});
Route::domain('www.example.com')->group(function () {
// remaining routes declared here
});
maybe this will fix the issues?