Courgette problem

Could they be the male flowers, as they appear first.

I have to ask, why do you have it in the greenhouse? It should be outdoors by now, in a pot or in the ground. The flowers need insect pollination to do best. This is not guaranteed under cover. I think that, if you prefer to keep it in the greenhouse, you should have used a soft paint brush to do this artificially. Another cause might be erratic, watering. the plant may be under stress, due to lack of regular moderate watering (and lack of liquid nutrient supplement incorporated, if in a pot), as opposed to the occasional overwatering to drowning point. Try it outdoors in a border, or in a container.