really need help with 4 servos with the arduino

ok here is an up date. I replaced 2 of the pots. and then i tryed this code again

#include <MegaServo.h>

MegaServo servo1;
MegaServo servo2;
MegaServo servo3;
MegaServo servo4;

int potpin1 = 0;  // analog pin used to connect the potentiometer
int potpin2 = 1;
int potpin3 = 2;  
int potpin4 = 3;

int val;    // variable to read the value from the analog pin

void setup()
{
  servo1.attach(9);  // attaches the servo on pin 9 to the servo object
  servo2.attach(10);  // attaches the servo on pin 10 to the servo object
  servo3.attach(11);  // attaches the servo on pin 9 to the servo object
  servo4.attach(8);  // attaches the servo on pin 10 to the servo object
}

void loop()
{
  val = analogRead(potpin1);
  val = map(val, 0, 1023, 0, 179);    
  servo1.write(val);
              
  val = analogRead(potpin2);
  val = map(val, 0, 1023, 179, 0);    
 servo2.write(val);
  
  val = analogRead(potpin3);
  val = map(val, 0, 1023, 0, 179);    
  servo3.write(val);
  
  val = analogRead(potpin4);
  val = map(val, 0, 1023, 0, 179);    
  servo4.write(val);
  
  delay(15);
}

it works.........................but i dont know why but 2 of the servos sake a little for then i would like. but there is no bleeding over as far as i can tell. The only different on the pots is that the ones i was using before were big and the ones im using now are little. i dont know if that maters or what, but something is different. any thoughts on this?