I do not know what happened here. The pepper was doing fantastic and then I looked and it was completely drooped. Not dead, just ALL leaves were limp. Water level was fine. (Earth box) and then I looked and found this on the bottom of two peppers. There is a possibility that too much Epsom salts were sprayed on them by a well meaning helper, could that have done this?
Here is a link about blossom end rot. But, there may be more going on here because you said the plants were drooped and all the leaves went limp. So it could also be over fertilization as mentioned in the article. http://hort.uwex.edu/articles/blossom-end-rot
I learned last year that peppers like bone meal as if it is crack cocaine. Just a bit (maybe a tablespoon every two weeks) -- they FLOURISHED - and I had a bumper crop. I haven't seen BER on peppers, but often fight it with my tomatoes - I always thought it was because the fruit got wet when it was setting.