Internet slow on only one computer

I have Cox for internet and lately the internet on one of my windows computers (wired) is really slow. Until about 2 or 3 weeks ago I was getting upwards of 30 Mbps download (paying for 25) according to speedtest.net.

Then a few days before Cox doubled internet speeds in my area (Story Link) my internet speeds dropped severely. It hasn't bothered me too much until I tried to download steam games and was only getting 1.1Mbps down on steam. I went to speedtest.net and was getting 9 Mbps now 0.5. I checked another computer (wireless) and it got 35 Mbps. I then checked my phone (wireless of course) and it got 46 Mbps.

This makes me think it's either hardware or software on my computer that is making is slow. Is there any way to fix it?

Edit 1: Now 0.5 Mbps