The blades MUST spin oppositely. One of your motors is plugged into the 4-in-1 incorrectly.
The right motor goes into the upper slot, with the black wire on top. "MAIN MOTOR R" the + sign shows where the orange wire goes.
The left motor goes into the lower slot, with the orange wire on top. "MAIN MOTOR L" the + sign shows where the orange wire goes.
The upper rotor spins counter clockwise.
The lower rotor spins clockwise.