Help with robot arm!

Hey everyone!
Im doing robot arm 3DOF controlled by potentiometer . My robot contains 5 servo, but I get one problem :
I can control smoothly 3 servo, but after I add the 4th servo . I could not control any servo by potentiometer
My code va picture attached below

#include <Servo.h>
Servo myservo1;
Servo myservo2;
Servo myservo3;
Servo myservo4;
Servo myservo5;
int bientro1=A1; // potentiometer
int bientro2=A0;
int bientro3=A3;
int bientro4=A4;
int servo1=7; //the base
int servo2=8; //
int servo3=9; //
int servo4=10;
int servo5=11;
int goc1,goc2,goc3,goc4,goc5; // degree
void setup()
{
myservo1.attach(servo1);
myservo2.attach(servo2);
// myservo3.attach(servo3);
myservo4.attach(servo4);
myservo5.attach(servo5);
}
void loop(){
goc1= analogRead(bientro1);
goc1= map(goc1,0,1023,0,180);
goc2= analogRead(bientro2);
goc2= map(goc2,0,1023,0,180);
goc4= analogRead(bientro3);
goc4= map(goc4,0,1023,0,180);
goc5= analogRead(bientro4);
goc5= map(goc5,0,1023,0,180);
myservo1.write(goc1);
myservo2.write(goc2);
myservo3.write(goc2);
myservo4.write(goc4);
myservo5.write(goc5);

delay(100);
}

I can control smoothly 3 servo, but after I add the 4th servo . I could not control any servo by potentiometer

The typical reason is an inadequate power supply. The servos need to be powered from a good external power source. Don't power from the arduino if that is what you are doing.