As a seasoned web developer and server management professional, I have gained extensive hands-on knowledge and insight into the intricacies of Magento 2, PHP-FPM processes, and CentOS 7, all of which will be invaluable in troubleshooting and resolving your issue promptly. I have successfully tackled similar challenges in the past, and if there's one thing I've learned, it's that every problem is unique. Therefore, my approach would involve a careful examination of your website's architecture to identify the underlying cause resulting in the unwarranted increase in PHP-FPM processes.
Moreover, having worked with various custom Magento extensions throughout my career, I am well-versed in diagnosing issues specific to these applications. This trait of mine would greatly aid me in pinpointing the problematic extension and finding an appropriate solution for it.
Lastly, communication is key when dealing with technical problems, especially when explaining complex issues to non-technical audiences. You can count on me to explain the problem as clearly as possible and articulate the proposed solution effectively so that you are not just kept informed but also empowered to make informed decisions. Rest assured, your Magento 2 site will be running optimally again under my care.