Female only Courgettes flowers

I'd appreciate any advice - especially if there's something I can do to rectify the problem...

I'm growing three courgette plants of the same type (could check back to find out what type they are if that's relevant). All three are producing copious amounts of female flowers but hardly any male flowers so the courgettes are failing to develop (due to lack of pollination I guess) and are dying off at a couple of inches length. We've had just one courgette develop into an edible vegetable all season (I assisted in pollination with just about the only male flower we've seen). I'd estimate about 20 - 25 courgettes haven't developed.

Whatever type they are, the courgettes are alledgedly suitable for outdoor growing and are supposed to yield heavily. They look like healthy, bushy plants (have grown courgettes many times in previous years without problem), can't see any infestations or other obvious issues, they are outdoors and in full sun for about 75% of day. They are well-watered with some feeding.

What's going on?

 

Hi AJ, I've got no idea either, might be the plants are under stress with the hot weather, are they getting enough water at the roots?

 

Thanks for your reply. Yes, I'd say they are getting enough water.

All three plants are planted in our home-made garden compost with added Growmore granules. This approach is working well with other potted plants, incl some edible crops, but I still wonder if the lack of male flowers is something to do with the compost.