Vitamins/Medics for better breeding results

hello friendsPlease advice for best vitamins or medicines currently available internationally for getting good breeding results. For the last three clutches from my almost all parrots; the result of hatching is only 25-35% (5 eggs and 1-2 successful). Only English budgies giving 80% results. I need details along with price and output/results. For the coming at least 6 months season will be very suitable for breeding birds in of Pakistan.ThanksAmir Usman Malik