twin brushless ESC wiring

[HighKalibre]

I've got a project in the works involving 2 MMM's each running a 1515 1y. I've come upon something that I'm not sure if its a snag yet or not.

last night when I was starting my unslow harness. I had the ESC's plugged into the servo y-harness which was hooked up to the rx. I wanted to check the esc for function and hooked one pack up to one of the esc's.

To my surprise both ESC's turned on. I'm fairly certain this has to do with the BEC backfeeding power through the y-harness into the other ESC turning it on. Is this a issue with the y-harness. Or would I just cut the red wire on one of the y-harness legs to eliminate this?

Thanks in advance