PS3 lagging

We are running 2 PCs 2 phones on WIFI and 1 PS3. For the PC and PS3 they are both hardlined for Cat6 and my girl and I game together all the time on either or both PC and PS3 at the same time. My problem is when I have downloads that need to be done or any videos our PS3 just drops heavy on its connection yet the PC works flawless. Our Nets are at a 21mbps down and 2.5mbps up stream we both game fine and dont suffer one bit when loading game servers or downloading in game(CS custom content etc) Any ideas on what is happening here it would be nice to have them splitting the net evenly and not have her lag out.

PS: when we have friends over on their phones our net does fine even if 5+ phones are on Facebook or youtube in HD 

if your router supports packet prioritization or something like QOS try to ready about that.

I found out it is a Steam server issue for some reason the Dallas server bottle necks so it has absolute internets for some reason Origin and other services and sites didn't do it back at all. All is good now thankyou for the idea however