Well the one thing I can think of is that you have a motor that has a bad winding (open or short). You need to find it to stop burning ESCs. Maybe you know which motor was connected to the ESC that burned up. Try setting it aside and testing the others.
Open motor legs (ESC disconnected) are easy to check for. When measuring a good motor, a normal ohm meter should show a dead short from each leg to each other leg (AB, AC, BC) because the resistance is less than 1 ohm.
Shorted legs are harder to check for. You need an ohm meter that goes down to 1/10th ohm or even less. I have checked resistance by using an automotive bulb (1156 or 2156) and a 3 cell lipo and an amp meter all in series with a pair of motor legs to run about 2 amps through the pair of legs. With that connected, measure the voltage across the motor legs. Resistance = Voltage / Current. Measure all three leg combinations for the motor (AB, AC, BC) and they should all be about the same and probably 0.1 to 0.3 ohms.