Code for three conductivity probes

Dear all,

For my project I need to connect three analog conductivity probes to an Arduino Uno. The values then need to be displayed in a excel file at the same time. For the moment I already do this with one probe. All the probes have a connection to the 5V pin, the GND pin and one of the analog pins, for the first probe this is A0. Below is the code I am currently using:

#include <rExcel.h>
const int analogInPin = A0;  // Analog input pin that the potentiometer is attached to
const int analogOutPin = 9; // Analog output pin that the LED is attached to
int sensorValue = 0;        // value read from the pot
int outputValue = 0;        // value output to the PWM (analog out)
long idx = 0;                // index
int outputTiming = 1000;    // packet sending timing in ms 
// important: this dermines the output timing
float a0;                     // A0 pin reading
float rnd;                    // random number
char value[16];              // written or read value
rExcel myExcel;                // class for Excel data exchanging

void setup() {
  Serial.begin(115200); // the bigger number the better
  delay(1000);
  // rx buffer clearing
  myExcel.clearInput();
  myExcel.clear("Example", "A11:F112"); // clear cells in A11:F70 area of 'Example' worksheet
}

void loop() {
  static unsigned long  loopTime = 0;
  static unsigned long  time1 = 0;
  int ret;
  loopTime = millis();
  // Output Task
  // Arduino acts as client making requests to Excel
  // instructions performed each outputTiming ms
  if ((loopTime - time1) >= outputTiming) {
    time1 = loopTime;
    // read the analog in value:
    sensorValue = analogRead(analogInPin);
    // map it to the range of the analog out:
    outputValue = map(sensorValue, 0, 1023, 0, 5000);
    // change the analog out value:
    analogWrite(analogOutPin, outputValue);
    float value = sensorValue * 5.00 / 1024;
    // print the results to the serial monitor:
    Serial.print("sensor = " );
    Serial.print(sensorValue);
    Serial.print("\t output = ");
    Serial.println(value);
    myExcel.writeIndexed("Example", idx + 11, 1, "%date%"); 
    // write %date% (that will be converted in current date) to worksheet 'Example' row 'idx+11' column '1'
    myExcel.writeIndexed("Example", idx + 11, 2, "%time%"); 
    // write %time% (that will be converted in current time) to worksheet 'Example' row 'idx+11' column '2'
    myExcel.writeIndexed("Example", idx + 11, 3, idx);      
    // write idx to worksheet 'Example' row 'idx+11' column '3'
    myExcel.writeIndexed("Example", idx + 11, 4, value * 1000, 2);  
    // write the value from A0 pin to worksheet 'Example' row 'idx+11' column '4' with two digits as decimals
    //myExcel.writeIndexed("Example", idx + 11, 5, rnd, 2);   
    // write a random value to worksheet 'Example' row 'idx+11' column '5' with two digits as decimals
    idx++;
    delay(1000);
  }
}

What needs to be changed to the code above so it works for three probes? My other question is regarding the splitting of the ground pin, as there are only two GND pins on the Arduino board. Is it okay to split one GND pin to two probes with a breadbord?

float a0;
float a1;
float a2;

remove the delay(1000); no reason to use it