Wn2500rp apple streaming problem

Funnily enough through VPN it does work. I have exactly the same setup as you guys. 5ghz router extender and 2.4ghz extender to devices. If i do a speedtest I get 24mbps with my iPad, which should be enough for streaming, though streaming is very slow. Then I activate my VPN from school and it works but speedtest remains the same... I recently changed the configuration because I wanted more speed as I have a 125mbps connection. Prior to this, I had 2.4 router to extender and 5 extender to devices, also fast lane. Back then it worked! Though I could only hit 60mbps on my computer, now 100. Back to our issue, I first thought it was about the 300mbps vs 145mbps but it makes no difference. Tried WMM, QoS no change. Like I say, the VPN part is interesting!