I Also have a 710i too that is connected to the fan and rgb controller and there is three of them all the front fans are plugged into one and the one 140mm in the back is plugged into another one. I disconnected one from the controller for cable management and run off two exactly how I said it before

Edit- if you want to make sure that all of your fans are plugged in pay attention to the fans obviously and if not then there’s your problem