Sorry @jesselat - I should have explained better.
The white LED outptut could indicate the Leak detected failsafe has been triggered:
sequence_failsafe_leak = DEFINE_COLOUR_SEQUENCE_FAILSAFE(WHITE);
I found the link on this thread related to a similar topic.
Do you get the Leak detected alarm in QGround Control? If you disconnect the leak sensor from the Pixhawk, the fault may clear?