server drain

i am using this plugin on a realtors website with a customized js search interface: http://viequesrainbowrealty.com/searchpg/
it works great except for the fact that with the latest two releases of wordpress it slows down site performance to a crawl.
any ideas what could be done about that?
i would greatly appreciate some help.
thank you!

https://wordpress.org/plugins/wp-custom-fields-search/