Could be any number of things, depending on temps, moisture, etc, all things that are impossible to tell without a little background info.

I planted in Sept 28th 2005 a row of green bell peppers. I had the going well due to warm Fall temps. Grew to about 6 inches, then pretty much stopped in height about 1.5 months later due to cold temps. Lost the entire row when temps dropped down below 32 for 2 days this past week. Lost my tomatos also. :( But then again, they are not winter crops. Carrots, parsley, turnips, beets and some lettuce are in now and growing fine with cold temps.

My first hand experience growing peppers have been taking into consideration different factors...
One is the right pH for such
Temps - - - -
they like it evently to set fruit ( for this I last grew them in cold frames / green houses ...

And also very important is the watering they have to have even watering.

One of the easier variaty to grow is the Italian at least for me those did wonders.

The first year I grew peppers, was in a very fertile soil and had been dormant for 2 -4 handfull of years so that along with regular watering ( I then must admit I used miracle grow) I don't anymore .. I had beautiful plants peppers ( Ivory was very prolific 2 + ft. plants) -
-Since I have grown peppers organically without chemicals and just this year I had better success with the cold frames/ greenhouses. I will try the row covers this coming year.
A combo of all factors is a key to great pepper crop!

I hope this helps :)!

Having 3 mules we spred the manure over the garden this fall hope that helps..also over the rhubarb..