Add mask for multiple faces

Question

I am trying to add mask for every detected face:

import os
import sys
import cv2
import datetime
import numpy as np

os.system("raspistill -w 1920 -h 1280  -o faces_to_detect.jpg")

imagePath = "faces_to_detect.jpg"
cascPath = "haarcascade_frontalface_default.xml"
faceCascade = cv2.CascadeClassifier(cascPath)
image = cv2.imread(imagePath)
gray = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)

faces = faceCascade.detectMultiScale(
    gray,
    scaleFactor=1.21,
    minNeighbors=3,
    minSize=(18, 18),
    flags = cv2.cv.CV_HAAR_SCALE_IMAGE
)

print("Faces on pic: {}.").format(len(faces))
faces_img = cv2.imread("/home/pi/Room/faces_to_detect.jpg")
mask = cv2.imread("/home/pi/Room/mask.png")
rows,cols,ch = faces_img.shape

for (x, y, w, h) in faces:
    cv2.rectangle(image, (x, y), (x+w, y+h), (0, 235, 0), 2)
    rows,cols,ch = faces.shape

    pts1 = np.float32([[x, y], [x, h+y], [w+x, y]])

    pts2 = np.float32([[0, 0], [x, 0], [0, x]])

    M = cv2.getAffineTransform(pts2,pts1)

    dst = cv2.warpAffine(mask,M,(cols,rows))

    result_img = cv2.addWeighted(dst, 0.8, faces, 1, 0)
    #cv2.imshow("Faces found", image)
    #cv2.waitKey(0)
    print(x,y,w,h)

cv2.imwrite("/home/pi/Room/replaced.png", result_img)

Problem which I am trying to solve: the mask appears for only one face (I want to add a mask to all faces I detected). Any helpful info will be great. Thank you!