live/studio desk problems.. urgent

i have just got a allen and heath zed24 desk, it is connected to hs80 studio monitors, i can only change the volume of the left speaker with the main out faders, the right speaker is still producing sound but much quiter, with no bass and i can still hear music only from the right speaker when the faders are all the way down, 

please can anyone give me some advice, i haave a gig and recording to do soon

thanks

matty 

And are you using any Hercules DJ devices with this mixer and speakers ?

May I suggest to first check your cables and connections ?