I am going to assume it is a wordpress blog?
Firstly, is the traffic real or just bot/crawlers? These bot traffic and crawlers can hamper your web server's resources heavily, thus causing your website to load slowly.
Install the following 2 Wordpress Plugins:
1) Bot Block or StopBadBot
2) WP Fastest Cache
If possible, buy the premium license of WP Fastest Cache and use the image optimisation tool. Optimise all images and you would save lots of kilobytes, thus making loading speed a breeze. Then enable all minify js, css, and other options. Enable caching too. Your website speed should improve drastically.
Point to take note: if your website is an ecommerce site, you may want to email the plugin developer for advice. Caching certain parts of an ecommerce site could cause some issues with the shopping cart and such.
EDIT: You're using too many plugins. I'm only using WP Fastest Cache and they have all the features you've mentioned. I'm not related to the developer of the plugin nor am I trying to spam it here. You may want to check if WP Super Cache has similar options to those other plugins you've installed as more plugins means more codes being inserted in each page/post.