The secrets of breeding and diet is not necessarily with the human managing the breeding techniques but rather with the individual pair of birds and observation! The trick is in record keeping (making note of these observations,) very closely with each pair that you manage. Starting from a hatchling or when you acquire them. Recording weight gains-losses-size-color-activity of each bird in your aviary is "priceless." There is NO silver bullit in breeding birds, no "special diet" or pellets that will assure you of anything.
As a rule of thumb I always feed my birds a healthy diet all year long. That includes the proper nutrition to sustain their activity in all seasons and weather conditions. Affecting the birds are their exercise, being more active in the times when it is warmer up here in Michigan, and declining when they are "Effected by the Changing Weather" (or the waning or waxing of the moon[1].) It is the MOON position that causes my birds to go into a brooder mentality. By record keeping I can tell when these periods are acting on the philological changes in the birds and respond with minor diet "accents." By accents I mean certain foods that aid their reproductive processes and also benefit the production of eggs and nutrients that will be beneficial to the offspring if that is the product. Again these accents are just subtle and not in masse, or put plainly, nothing major. Change is not good when dealing with any parrots, especially when dealing with their diet.
Stick with the basics and then use good common sense when giving additives/vitamin/mineral supplements. Use this list when prescribing a diet (this the best I have found.)
http://www.freewebs.com/macaw672/feedingyourparrot.htmAgain this is by far the best parrot diet I have ever come across, and her list also includes an explanation of the how's and why's for each of her diet recommendations with links. I have been using this diet with all my birds for years now and have a "Marked" improvement in every area that I have been recording. My birds are happier, healthier, more active breeding, terrific babies, better attitudes with companion (pets), all are good weights (those who needed to loose weight have[2] and others that needed to gain have also) and managed great blood counts with every Vet exam that I have taken them to. My vet has adopted this list and whole heartedly agrees with every recommendation she has made. I do have differences in opinion with a few of her comments but I have learned to understand why and how she makes these points and agree to disagree in them.
[1]
http://en.wikipedia.org/wiki/Lunar_phase[2] I had a troubling Scarlet Macaw Adult Male that was "overweight" you know when you look at him he had cleavage? Well I couldn't get him to loose the weight and his health started to show a marked digression. After 6 months on her diet he is now optimum weight, healthy and active again. His other problems are starting to come around. So in this case she saved his life!

NOTE THE CLEAVAGE BETWEEN HIS LEGS