experiencing lag when i fire up twitch

So I build myself a new comp yesterday (skylake 6700k with 32 gb ram and a 970 gtx) and I'm experiencing this annoying behavior:
- solo I have my settings at ultra and get anywhere between 45 and 70 fps in orgrimmar
- while triple boxing I have my settings at high on the main and good on the 2 alts, and get about the same fps range in org
- when running OBS I hardly notice any drop in fps

but in both the solo and boxing scenario my fps drops to 15 when I open a twitch stream (in chrome), under win 10, but playing a video on my left screen doesn't cause any fps drops

anyone a clue what might cause this?

edit: turns out that it is chrome that is causing the issue on windows 10, plenty of reports of the same behavior through a quick google (like this reddit thread)

Although you have already found an answer to your query, I would like to throw this out there for everyone, as I've found it pretty close to Godsent for watching streams while boxing:

There is a nifty little command line program called Livestreamer. It'll allow you to feed a stream straight to VLC/MPC/a few other players instead of using the ridiculously resource hogging default flash player on twitch. With a quick test it appears (for me atleast) to only require about 10% of the CPU power required for watching normally on Twitch.

You can either launch the stream through your command line manually, or for firefox users there is also an add-on that adds a right-click functionality for twitch to launch streams with it.