What's happening to my Sweet Peppers?

I have loads growing, but as they get bigger, the first did this.

Any advice or helps to stop this happening?



And another is starting to do similar.

 

I've had that happen as well. I usually put it down to scorch.
The sun coming through glass can almost cook them on the plant.

 

Looks like Blossom End Rot (BER)
Have a Google for it.

 

As Alice suggests most probably BER. Though I wouldn't rule out Pete's suggestion regarding scorch since I can see water on the GH windows and if you get splashes on the fruit followed by hot sun the water drops on the fruit act like a magnifying glass.

Peppers seem to require a different feeding regimen than tomatos with less potassium.
Here's a couple of links that may help >

http://www.gardeningknowhow.com/vegetable/pepper-blossom-end-rot.htm
http://www.allotment.org.uk/fertilizer/npk-fertilizer.php