So I don't want to overfeed my new IRN so I want to know how much seed (eg 1/2 cup, or more/less) of seed per day. (i'm feeding them heaps of vegies so I've got that covered.)
I typically try to feed just over the amount my birds will eat within one day.... which, depending on the birds, that's between 10-15% of their body weight in dry food alone - not counting fresh food.
If I see them eating more food than what I normally provide, then I'll up the amount if need to, to ensure that they'll eat most of it within a day. I'd rather slightly over-feed than under-feed.
You can also feed pellets (as Mikey suggested), some fruits, the occasional cooked eggs, healthy grains and healthy legumes in addition to what you are already feeding.
I have thought about pellets, infact i do have pellets for my budgies which i will give with their seed or have a pellet day. I know everyone reccoments pellets but looking at rough nutritional contents of various seed and pellet mixes though, in some brands i don't see much difference except for protein content, which i figure, like you said, feed an egg occasionally would make that difference. (plus vegies and fruit for vitamins) im only hesitant with pellets because they're quite expensive. do you find there's a noticeable difference with your parrots health in seed vs pellet?
The better question is, if pellets are supposed to be a "complete diet" and seeds are not a complete diet, are your birds getting the necessary nutrients that they require from a non-pelleted diet? If you can't answer that, you should probably be feeding pellets.
I've actually noticed that my birds eat less pellets than seeds. My flock of 4 cockatiels eat, on average, less than 30 grams of pellets per day. However, when I feed them seeds, they require at least 45-50 grams of seeds. Seeds have more waste than pellets do, however pellets are more filling than seeds are. Consider how much seed you may be wasting vs how much pellets. Do pellets still seem that expensive?