You took pictures of a concert and missed the band?
(Giving away my age, that's what I'd call a disco!)
That looks like a really difficult situation to shoot in. I've tried a few concerts and having a dark background tends to help but you've just got open space and those brick walls. Lots of low level background light. Stick at it, my guess would be that pictures from behind the decks into the crowd or more from the sides if you could shoot against a darker background may have worked well when working without the flash.