I think it is much more likely to be related to or associated with the fact that the sex of the flowers produced by the plant is not going very well .
Nature times the female flower to start to open when the make flower starts to produce pollen ( or the other way round .)
Look up pollinating of curbits & IIRC you'll see what I'm on about
BER ...Blossom End Rot .
The flower end of the courgettes & curbits hold a lot of bacteria , cool damp conditions this leads to the ends of one of the sexes going rotten.
Once you have set flowers ,,, those flowers starting to turn to courgettes you can feed the plants with a pint of correctly dilute tomato feet once a week .....watered in & around the main root stem .
We have been laying the low lying courgettes on pieces of clean white plastic to see if we can get over the problem , for we too have only be able to get pencil thick 3 inch long courgettes so far this year .
Come to think of it I'll have a read up of old Percy Throwers gardening encyclopedia book from the early 1960's to see what he recommended .