I have three computers in my home. My old computer is a lenovo w530 running windows 10 and my new computers are a 13'' and 15'' inch macbook pro 2015.

All computers are connected to the same wifi router.

if I connect my windows machine and my 13'' macbook pro to www.speedtest.net it report a internet connection speed of Download: 57.65 Mbps Upload: 57.96 Mbps

when I do the same thing on my 15'' macbook i see connection speed of Download: 3.2 Mbps Upload: 0.59 Mbps

Why is 15'' mac so slow for wifi as compared to my 3 year old windows and 13'' inch macbook pro?

Edit:: Here are the details requested below

RSSI: -37dBm
Noise: -93dBm
TxRate: 117 Mbps
MCS Index: 15
CountryCode: US