Yes you do! Otherwise you´ll have 3 times the amount of current passing through your control board and then it needs to and that is not good! The best thing you can do is:
if you look closely at those BEC plugs you can see that there are three black pins holding the golden part inside. if you just lift up the one of the red wire (i believe it is the middle one) then pull out the red wire you will have the complete golden plug with your wire out of the plug and for any other need in future available again without soldering and cutting. I hope you got what I mean.
Linear stabilizers are even more OK. It's common practice to use more stablizers parallelly if you need more current draw. In fact, only one works (that one with the highest voltage), others don't work until the voltage drops to their upper voltage limit.
I have connected up the motors and done a calibration and they work fine except one. On low throttle 3 of the 4 motors spin up fine, however this one only moves around. It takes up to half throttle before it actually starts to move. Then can proceed to spin at a lower throttle, however does not seem to be spinning as fast as the rest. They are all on the same timing mode. Is it possible for that motor to be getting less power than the rest?