You can install the following utility on your computer:
http://www.tp-link.com/en/support/download/?model=TL-PA6010&version=V1#tbl_b

Then you connect your computer directly to your WPA2220 and run this utility.
This utility will help you check the real powerline speed among all your powerline adapters.

If the real powerline speed is very slow like 40Mbps (normally it should be 150Mbps or more), then it means there are too much electric noise in the powerline circuit.
You can check your appliances to see which one may affect your powerline devices' performance.