It has nothing to do with your server performance, but the pipe.
2 weeks ago you may not have that many users online to fetch the bandwidth from the server, but now as you have, with loads of heavy elements on the frontpage (9+ MB is ridiculous high), if you are considering scoring as bad, then let me tell you one thing, scoring is not bad at all, I have seen plenty of popular sites with even less scoring and still working A-OK.
Now for optimizing the
front page, you need to
1: optimize the images, as I assume you have just placed the raw images in slider, with each image nearing 2MB you are loading 8MB upfront, though there is a slight fault for the slider as well as it was supposed to be loading images as slider moves rather downloading all images first before moving slider.
2: use a CDN, use CloudFlare free package, they will cache the heavy elements (Images) on their nodes so rather they coming from your server, they will be served via CDN making it faster for users to fetch the data.
3: for that many users, I am assuming you must still be sitting on a 100Mb/s pipe, which I would recommend to upgrade to 1000MB/s to avoid he bottle neck in transferring data.