Help link cdjs 3000

Hello, I need some help with this: I have 4 cdjs 3000 linked and the v10. On each cdj a different usb with no name. I have some difficulty in found out which flash is on use. Yes the flashing one is on use I know that, but on which cdj? For example the flash on cdj 1 can be flashing (means on use) but how can I know from which of the cdjs? Mostly on this case for example when I have to take off 3 of the 4 flash from the cdjs how can I make sure I don't take off the one which is playing? Yes also there is the safety reject, but if hold the button it get rejected and the track stop. Sorry for the confusion but I hope you understand what I am asking. Thank you,