Problem with Multiples Airport Extreme

Hi All

For your info, i have 5000 square feet house single story

I have setup 4 airport extreme divided to 4 different location of the house

Let we call the airport as AP1 AP2 AP3 and AP4

All airport extreme are connected by wire to the Cisco router that have 16 port

All AP have same ssid and password

I have a problem

Let see, i have a laptop connected to AP1 and i move the laptop to AP 3 location without turn off the wifi

Somehow, maybe the AP1 signal still have at AP 3 location.

When i make a speediest at AP1 location its give me full internet bandwidth by provider such 24 Mbps

But when i move to location AP3 where i assume that AP1 signal still available but not full

When i do the speediest, its give me 1-2 MBbs

How can i overcome this problem without to turn off back the wifi in laptop and turn on back

mazhar