There is a major issue when using WPML (Multilingual plugin for WordPress for website translation) that your website suddenly starts consuming too many CPU resources and Increasing Server REsponse time and hence increases Time yo First Byte (TTFB). Which again leads to the slowdown of the website.
Why is that happening..?
Honestly saying, WPML is not a really good plugin to choose if you have a lot of pages because it uses multiple simultaneous query requests and cron jobs to process translation.