Using the Adafruit ADS1115 16-Bit external ADC chips

I am currently trying to run a very basic program to get the chips working before I apply this to what I actually want to do. I have downloaded the Adafruit_ADS1x15 library and have input 4 analogue signals into the chips.

From what I have read so far, there are 3 main options for taking readings. Compirator, differential and single. I think I want to use single as this will let me use all four inputs individually. However, the problem I am having is that when there is a signal change detected in one of these inputs, the signal changes in all of the inputs. Has anyone used this and is able to give me some advice as to what is going wrong?

So far, everything I have done (mostly modifying the existing examples) has been registered by my Arduino board.

#include <Wire.h>
#include <Adafruit_ADS1015.h>

Adafruit_ADS1115 ads;  /* Use this for the 16-bit version */
Adafruit_ADS1115 ads1115(0x49); // construct an ads1115 at address 0x49
//Adafruit_ADS1015 ads;     /* Use thi for the 12-bit version */

void setup(void)
{
  Serial.begin(115200);
  Serial.println("Hello!");

  Serial.println("Getting single-ended readings from AIN0..3");
  Serial.println("ADC Range: +/- 6.144V (1 bit = 3mV/ADS1015, 0.1875mV/ADS1115)");

  // The ADC input range (or gain) can be changed via the following
  // functions, but be careful never to exceed VDD +0.3V max, or to
  // exceed the upper and lower limits if you adjust the input range!
  // Setting these values incorrectly may destroy your ADC!
  //                                                                ADS1015  ADS1115
  //                                                                -------  -------
  // ads.setGain(GAIN_TWOTHIRDS);  // 2/3x gain +/- 6.144V  1 bit = 3mV      0.1875mV (default)
   ads.setGain(GAIN_ONE);        // 1x gain   +/- 4.096V  1 bit = 2mV      0.125mV
//   ads.setGain(GAIN_TWO);        // 2x gain   +/- 2.048V  1 bit = 1mV      0.0625mV
  // ads.setGain(GAIN_FOUR);       // 4x gain   +/- 1.024V  1 bit = 0.5mV    0.03125mV
  // ads.setGain(GAIN_EIGHT);      // 8x gain   +/- 0.512V  1 bit = 0.25mV   0.015625mV
//   ads.setGain(GAIN_SIXTEEN);    // 16x gain  +/- 0.256V  1 bit = 0.125mV  0.0078125mV

  ads1115.begin(); // Initialize ads1115
  //  ads.begin();
}

void loop(void)
{
  int16_t adc0, adc1, adc2, adc3;

  adc0 = ads.readADC_SingleEnded(0);
  adc1 = ads.readADC_SingleEnded(1);
  adc2 = ads.readADC_SingleEnded(2);
  adc3 = ads.readADC_SingleEnded(3);
  Serial.print("AIN0: "); Serial.println(adc0);
  Serial.print("AIN1: "); Serial.println(adc1);
  Serial.print("AIN2: "); Serial.println(adc2);
  Serial.print("AIN3: "); Serial.println(adc3);
  Serial.println(" ");

  delay(250);
}
Adafruit_ADS1115 ads;  /* Use this for the 16-bit version */
Adafruit_ADS1115 ads1115(0x49); // construct an ads1115 at address 0x49

That suggests that you have two of the boards attached - do you?
It also suggests that one of them has an address of 0x49 - does it?
Why set the gain for the board at the default address, but not the one at 0x49?
Why "begin" the board at 0x49, but not the one at the default address?
Why read the board at the default address, but not the one at 0x49?