unplug everrything and start from scratch,

1. Your batteries in parallel?
2. Y harness. If you can, try switching the leads and rule out bad connection Example, if (esc,yharness branch) ESC1-1 and ESC2-2 and ESC1 works. Try ESC1-2 and ESC2-1. If ESC2 works, your harness is fine. IF it dont harness is bad.
3. Do both respond to calibration?
3. wire everthing BUT the motor and see if both LEDs respond.