Powerline kit speeds got slower? Help please

WD- Livewire Powerline A/V Network Kit

I bought a western digital powerline kit and for the first week or two speeds were great 15-20download and 10upload but now about a 3weeks-1month later the speeds have dropped to 4mbps download speed but upload is still the same. If I unhook the ethernet and just run wireless my speeds are 10-15mbps download. So that basically tells me there is something wrong with the powerline kit. Does anyone know what could be wrong?

Try connecting the two livewires to the same power socket, to see if you get a better transfer rate, also check if you have any other devices that my be introducing interference to the electrical wiring.