Unfortunately, I don’t know what could cause that. All I can recommend is to do some profiling and benchmarking to find out what takes the most time during a page load, and how that changes when you activate or deactivate the plugin. For example, are there more database queries when the plugin is active? Slow network requests? A lot of time spent running a particular PHP function?
can you recommend any plugin to do that ?
regards
Personally, I would use XDebug, but it’s a PHP extension and not a plugin. That might be too complicated if you’re not familiar with PHP development.
As for plugins, Laps looks pretty good, though I haven’t used it much. Query Monitor is a popular plugin that provides a lot of information.