courgettes

I am growing courgettes (defender) in pots, and they are going soft and rotting at the flower end. This has happened in previous years, not just because this summer has been very wet. I remove the flower head, and any yellowing leaves. Any tips please? 

I suspect this is because they've not been fertilised - possibly due to a lack of male flowers or a lack of pollinating insects due to the weather.

However, my courgettes are not rotting off even tho' I suspect they've not been pollinated - see my query re Courgette Parador