Can anyone tell me why my fruit is rotting on the stem? Aubergines and pumpkin have just gone to mush ! Why?

Noticed your question in 'unanswered questions' and was interested as the same is happening to some of my sweet peppers.
The answer to my question was that it was most likely botrytis caused by overcrowded conditions and too much watering (which pretty much matches my conditions).
Have you been doing overhead watering? Or just too much watering?
Have you allowed space for ventilation between plants?
If you are in the UK, haven't you had cool and wet conditions... this could explain why your plants have not developed as they should.