Laravel 8 Laravel迁移-此模式中是否有错误或写得不好的地方？

这是我的模式：

Schema::create('settings', function (Blueprint $table) {
            $table->id();
            $table->unsignedDecimal('custom_price', 6, 2)->nullable();
            $table->unsignedDecimal('custom_final_price', 6, 2)->nullable();
            $table->unsignedDecimal('custom_discount', 6, 2)->nullable();
            
            $table->enum('custom_discount_type', ['flat', 'percentage'])->nullable()->after('custom_discount');
            $table->dateTime('custom_discount_start_datetime')->nullable()->after('custom_discount_type');
            
            $table->dateTime('custom_discount_end_datetime')->nullable()->after('custom_discount_start_datetime');
            $table->unsignedDecimal('tax', 6, 2)->nullable();
            $table->unsignedDecimal('discount', 6, 2)->nullable();
            $table->enum('discount_type', ['flat', 'percentage'])->nullable()->after('discount');
            $table->dateTime('discount_start_datetime')->nullable()->after('discount_type');
            $table->dateTime('discount_end_datetime')->nullable()->after('discount_start_datetime');
            $table->unsignedDecimal('shipping_price', 6, 2)->nullable();
            $table->unsignedDecimal('shipping_price_add', 6, 2)->nullable();
            $table->timestamps();
        });

当我尝试迁移php:artisan时，会弹出这个错误

SQLSTATE[42000]: Syntax error or access violation: 1064 You have an error in your SQL syntax; 
check the manual that corresponds to your MariaDB server version for the right syntax to use near 
'after `custom_discount`, 
`custom_discount_start_datetime` datetime null after...' at line 1
(SQL: create table `settings` (`id` bigint unsigned not null auto_increment primary key, 
`custom_price` decimal(6, 2) unsigned null, 
`custom_final_price` decimal(6, 2) unsigned null, 
`custom_discount` decimal(6, 2) unsigned null, 
`custom_discount_type` enum('flat', 'percentage') null after `custom_discount`,
`custom_discount_start_datetime` datetime null after `custom_discount_type`, 
`custom_discount_end_datetime` datetime null after `custom_discount_start_datetime`,
`tax` decimal(6, 2) unsigned null, 
`discount` decimal(6, 2) unsigned null, 
`discount_type` enum('flat', 'percentage') null after `discount`, 
`discount_start_datetime` datetime null after `discount_type`, 
`discount_end_datetime` datetime null after `discount_start_datetime`, 
`shipping_price` decimal(6, 2) unsigned null, 
`shipping_price_add` decimal(6, 2) unsigned null, 
`created_at` timestamp null, 
`updated_at` timestamp null) 
default character set utf8mb4 collate 'utf8mb4_unicode_ci')

我不理解错误，如果有人能告诉我错误或不正确的语法来帮助我。谢谢