Humming sound on active speakers via Technics 1210 Mk5

Hi,

hoping someone can help as this issue is driving me crazy.

i have a DJ set up with 2 Pioneer CDJ 3000, pioneer A9 mixer and 2 technics 1210s Mk5 anniversary edition playing through Buchardt A10 Active speakers.

the problem is I get a deep rumble through the speakers when the needle is placed on the record and not actually playing. Even if the deck is turned off the rumble is there. It gets worse if I increase the volume on the mixer. Once I start playing the record it goes away, more or less, but if I increase the volume it comes back. I have the technics on an isolation platform (isoacoustics Delos) but it makes no difference.

the grounding cable is attached the grounding connector on the mixer but it makes no difference. I’ve tried moving it around but it makes no difference. 
 

it’s weird because the moment I take the needle off the record, there is no rumble at all. It’s only when I place it on the record without the record spinning. 
the active speakers are pretty close to the record player and there is no way to move them due to the DJ set up. 
 

this happens on both decks which are at opposite ends of the table. 
it’s driving me crazy and I don’t know if it’s electrical (the cables are all close together) or some other type of interference. 

if anyone has any thoughts or advice I’d be very grateful.

thanks again.