so i can't seem to get the sticks over 450 mhz

I have a gekkoscience usb hub, with 2 ports splitting 6 amps connected with a 200watt FutureBit power supply

I've put 3 into the hub and connected it to an old RaspberryPi3 got CGminer running no problem but no matter what i do i can't get them over 450mhz - according to the chart on page 3 i can go much higher than this