Game messing with my internet speeds and LAN.

I was in the main menu of the game, trying to download something on steam, getting 100 Mbs. Internet speed tests gave me 100 Mbs. Websites were having a hard time loading, even my routers webpage (hosted on my LAN) wouldn't open at all. Tried restarting router, computer, etc. I have everything wired together, fast router bought in the last year, Cat6 to a Gigabit switch, Cat6 to my computer. Fiber all the way to ISP. I get sub 30 ping in most games.

I closed the game out, and what do you know, suddenly websites are loading, download and internet speeds up to 300 up and down. WTF.