My code isn't adjusting the speed of one of the motors and i'm not sure why
If the left LDR is picking up more light than the right LDR, the left motor should be assigned a 'speed' of 80 whilst the right motor has a speed of 210. If the right one has more intensity, then the right motor should be assigned a speed of 80 and the left motor assigned a speed of 210.
  
  If they're both equal each motor should have a speed of 210 (although I dont have that included in the code). 


In code you would express this as

void loop() 
{
    int ldrReadL = analogRead(leftLDR);
    int ldrReadR = analogRead(rightLDR);
    int leftLDRread = ldrReadL;
    int rightLDRread = ldrReadR;

    digitalWrite(motorDirectionA, LOW);
    analogWrite(motorEnableA, motorSpeedA);
    digitalWrite(motorDirectionB, HIGH);
    analogWrite(motorEnableB, motorSpeedB);

    Serial.print("Left LDR reading: ");
    Serial.println(ldrReadL);
    Serial.print("Right LDR reading: ");
    Serial.println(ldrReadR);

    //assuming motorSpeedA is the left motor
    // left &gt; right 
    if (leftLDRread &gt; rightLDRread) {
        motorSpeedA = 80;
        motorSpeedB = 210;
    } else if( leftLDRread &lt; rightLDRread ) {
        //left &lt; right 
        motorSpeedA = 210;
        motorSpeedB = 80;
    } else {
        // left == right
        motorSpeedA = 210;
        motorSpeedB = 210;      
    }
}


Also note that this is a quite primitive form of a PID controller. You want to respond to environmental influences in some kind of way, for which a PID is for.

You might find these videos interesting:


https://www.youtube.com/watch?v=1pKJ-KcHZ8g
https://www.youtube.com/watch?v=VVOi2dbtxC0


Edit: The code was fixed, a wrong variable was used (the pin number vs the read value)