That sounds like poor pollination to me. Even though aubergines are self-pollinating (that is they have male and female parts in each flower) plants grown indoors need a bit of help to get it together - give the plants a gentle shake as if they're being blown by the wind, when the flowers are open. That should do the trick.
Well done to get them to that stage, marble size. Mine have been ever so slow to grow. I've one bought plant which has a large fruit on but the rest, sown at home are just producing large leaves at present
Went out today and discovered some marble sized fruit on a plant I'd sown, ever so exciting, how big should they get before they can be picked, the plants themselves aren't very big, prehaps 1.1/2ft tall, tops.
Size depends on the variety, Zoomer, but as a rule of thumb it's always best to harvest them a little early. A good test is to check the skin. If it's shiny, with a sort of sheen to it, it's pretty ready. It should also be still firm to the touch.
The variety is Black Beauty, Italophile, in anticipation I got out some Greek cook books today for recipe's, the fruit on the bought plant has lost it's shinyness, so, guess I've missed the boat with that one. It was about golf ball size, I'll wait for the others to get about the same size and pick whilst shiny.
Lost one - died off for no apparent reason. Three left - lots of leaves but no signs of flowers yet. Hmm. I think the light level has been far too low - but sudden bursts of sunshine may prompt some growth of flowers and fruit! Here's hoping.
Zoomer, this site http://www.simplyseed.co.uk/aubergine-seeds/black-beauty.html reckons they should get to about 12 cm when they're ready to harvest.
Thanks for the link Dovefromabove- my plants aren't very big, can't imagine they would support fruit that size, it's a nice thought though. Apart from toms and cues, most other plants I grow in the GH only grow to dwarf sizes.