WordPress Expert for Website Optimization

I am in need of a proficient WordPress professional to perform an in-depth performance evaluation of my website. The central task will be to pinpoint the plugin that's contributing to the slow operation of the site and assist in optimizing it. Additionally, the 'featured image' button on my 'custom post' projects has disappeared, so I’d like that restored.

Key duties:

- Implement a comprehensive performance assessment of the website to detect the sluggish plugin.
- Restore the missing 'featured image' button on the 'custom post' projects.

Here's what I'm asking for:

- Address both issues—site performance and the missing button—simultaneously.
- To avoid any user inconveniences, modifications should be done during off-peak hours.
- All necessary modifications will need to take place on the live site.

Ideal candidate experience and skills:

- Proven experience in WordPress development and customization.
- Ability to troubleshoot and fix performance-related issues.
- Familiarity with a variety of WordPress plugins.
- Strong awareness of optimal web performance trends and updates.
- Attention to detail and troubleshooting ability.

I look forward to getting my site back in top shape with the right expertise on board.