Extremely slow WiFi on iPhone 5/AirPort Extreme (gen 5)

Extremely slow wifi connection with iPhone 5 and AirPort Extreme (gen 5). Connection to my of laptop screams; can't even watch YouTube on iPhone. Tried different encryption settings and lots of other stuff. On speedtest, my download averages <500k, but my upload averages about 2.4 Mbps. My Lenovo laptop gets downloads as high as 18 Mbps at the same time I can't get anything on my phone. iPad has quick connection as well. Just have the problem on my iPhone 5 and my wife's iPhone 5. Desperate for help. Any ideas?