Oh you got the diskmark not the diskinfo...regardless though you seem to found your m.2 temps. And everything looks good. I am not sure what is happening. If your at 55C on one 35C on the other I see no reason to be throttling (assuming you check temps while benching). Even if you didn't though those benches look good for speed and regular windows use like downloading shouldn't stress your drive to much harder. I might even think it was a driver issue but again your speeds are really good.
So The next thing I would try is doing a speed test of your internet. Try this link below and let me know your results.
http://beta.speedtest.net/
We'll see if we can't narrow this down yet.