Sometimes you can cut a long story short:
1. Install only plugins you are going to use, do not leave them deactivated, delete them in this case.
2. Install . 6Scan security Plugin to see whether the plugins you are using are compromizing your site’s security and deal with them appropriately.
3. Offer links to sites who can meassure your sites loading performance http:///fpt/
4. install plugins like Wordfence and WP Firewall2 for neccessary protection of your site. Here we are not only talking plugins, themes can have the same security problems.