how to calculate quaternion difference

I have two sets of euler angles ([30,40,50] and [10,10,10]) and I want to compute difference using quaternion representation. Here is my code:

q1=angle2quat(deg2rad(30),deg2rad(40),deg2rad(50));

q2=angle2quat(deg2rad(10),deg2rad(10),deg2rad(10));

q3=quatmultiply(q1,quatconj(q2));

   [r,p,y]=quat2angle(q3);
   rad2deg(r)
   rad2deg(p)
   rad2deg(y)

The above code giving:

 12.1717

 37.4853

 29.6621

But actually I have to get 20,30,40.What is the wrong in mycode