Assuing they are standard boosters, try this. Place a booster approx half way between where you want it and the hub, but by a plug socket, then power on the booster, wait for the wireless light to come on and press the WPS button on the booster for at least 3 seconds, it will then flash Amber. Within 2 mins press the WPS button on your Hub for at least 3 seconds. Once connected the WPS lights should go out.
Worth a try.
EDIT: Assuming it works, repeat for 2nd booster.
you didn't say what else you have tried but standard to help is to split the 2.4/5ghz networks and also select the channels manually and see if that improves wifi many devices don't like the 2 networks combined.
you can alos try changing the wireless mode from 1 to either 2 or 3
if you have a hh6 your will see wireless mode set to default 1 try 2 or 3 - changes from ac to ac/n or b/g/n