Youtube constant buffering on Wifi?

So I've been having an issue with my S3 from T-Mobile in the past couple days. Normally youtube works just fine, but now recently it keeps buffering whenever it's on Wifi. I'm assuming it must be the connection because whenever I take it off Wifi, it stops and works just fine.

Is there some kind of issue with my Wifi? even though it has full bars. Never had this problem before.

 

So far I haven't had any issues on my pc. Yes multiple people using at once. But I was also on it once again today, my S3, the only one using the connection and it was still doing it.

Results for speed test
Wifi: Ping 12ms Download 2.09 Mbps Upload 0.82 Mbps

T-Mobile: Ping 37ms Download 25.32 Mbps Upload 5.10 Mbps

And that was with T-Mobile's reception at the time only on one little bar.