spoilt Milk

<p>About a month ago I purchased a 6pack pnp long life UHT milk, the 1st box that I opened was spoilt, the 2nd box was good initially and after a day it got spoilt, the 3 box was good and I used it within a day, I now opened the 4th box it's completely spoilt, I still have 2 sealed boxes, This was purchased at the vaal mall pick n pay, I do not have the proof of purchase, the best before date is May 2017 </p> <p>NB: I do store my milk in a cool place. </p>