well they usually drop off due to lack of pollination or dry air. do they have any greenfly problems as I find birds will peck/ eat these and this knocks the flowers off.
try spraying the actual flowers with a fine mist in the evening to help pollination too.

welcome to GoY too:o)

Thanks, a month later and they are doing well now, really thick foliage and keeping two families supplied. Spraying I think was the answer.

glad you have had a good crop :o)