Multi colour detection does not show centroid more than 1 object, Only show the centroid of Image which had largest pixel

Question

I am still new to OpenCV, i am trying to detect object of multiple colour as well as center of the object. The color i need to detect is Red, Blue and Yellow. My program able to detect different colour, but it can't detect centroid of the same colour. The object with the bigger pixel will take the priority. Is there anythings i miss or where can i improve in my code?

main.cpp

  inRange(imgHSV, Scalar(redLowH,redLowS,redLowV), Scalar(redHighH, redHighS, redHighV), imgThresred); //Threshold the image
  inRange(imgHSV, Scalar(blueLowH,blueLowS,blueLowV), Scalar(blueHighH, blueHighS, blueHighV), imgThresblue); //Threshold the image
  inRange(imgHSV, Scalar(yellowLowH,yellowLowS,yellowLowV), Scalar(yellowHighH, yellowHighS, yellowHighV), imgThresyellow); //Threshold the image

  Moments rMoments = moments(imgThresred);    
  double dM01_r = rMoments.m01;
  double dM10_r = rMoments.m10;
  double dArea_r = rMoments.m00;

 //Calculate area of Red Object
      if (dArea_r > 10000)
      {
       //calculate the position of the ball
        posX_r = dM10_r / dArea_r;
        posY_r = dM01_r / dArea_r;        

       //cout<<"The red object : X coodinate is "<< posX_r <<", Y coodinate is "<< posY_r <<endl;
       if (iLastX_r >= 0 && iLastY_r >= 0 && posX_r >= 0 && posY_r >= 0)
       {
        //Draw a red line from the previous point to the current point
        line(imgLines_r, Point(posX_r, posY_r), Point(iLastX_r, iLastY_r), Scalar(0,0,255), 10);
       }

       iLastX_r = posX_r;
       iLastY_r = posY_r;
      }
         imgOriginal = imgOriginal + imgLines_r + imgLines_b + imgLines_y;      

      //Check Object region in the image
      if (posX_r < 100)
      {
        cout<<"left side"<<endl;
      }else
      {
        cout<<"no"<<endl;
      }