Motor won't spin together, the other one is late

Hello everyone, Im new here. I would like to ask for your help please. I have Pixhaw 2.4.8 and F5550 (Hexacopter). I tried testing all the 6 motors, 2 motors start spinning at 4%, 2 at 5%, the other at 7%. So throttle at 5% the four motor spin together leaving the 2 motors not spin. Upon arming the, it wont fly instead it flip forward. What to do? Help please.

Have you read this?

Hi, already done this. Still the same :frowning: