Hey Slider,
Define high end strings.
I've been hacking acoustics for 35 years and never broke a low E string.
Check the nut and bridge for sharpness that may dig into the string.
Get, if you don't already have one, a chromatic tuner and use it to tune up.
Some acoustic guitars have floating bridges that you can adjust, side to side. When changing strings your bridge may have become out of alignment with the nut and put the string in a bind. That's another reason to change one string at a time and not de-tune the guitar all at once.
Unless you're just jack-hammering the strings, the low E shouldn't have any reason to break. It could just be a manufacturers flaw. I wouldn't fret it if it's not a recurring problem. If it becomes or is a frequent problem, send the guitar to a luthier and have them set up the guitar again. $20-40 bucks??
Also, I asked about high end strings. I buy $5-$6 dollar sets for my acoustic sixes and $7 dollar sets for my acoustic 12's. However, on my Rickenbacker 360/12 I buy
Pyramid Golds. Now, Pryamids are high end strings. Of course, the mention of Pyramid strings was to get you to listen to my
Rickenbacker!
**
Les