I'll be completely honest @kerimyth I am completely new to alliums and have yet to experience their problems. However, as with other bulbs, sometimes the growth for the year is determined by how they were cared for the year before, if cut back too early it might be that they did not produce enough energy to produce big blooms. Another problem could be bulb mining grubs like weevil. If the bulbs have been reduced in size? This may also impact on eventual plant / flower size. But that's a guess.
@theurbangardener, you may be right about me cutting them back to early!!! After I had cut them I just knew that I should have left them for longer!! I shall not touch them this year and see how they grow next year!! Thank you!! Xxx