Thank you so much for reconsidering potty training! I cannot even begin to tell you how big a relief it is to me that you did. I know he is not my bird but I love all birds, my own, other people's, the wild ones, all of them - and I worry when people are misinformed about their needs or capabilities. Now, I would suggest you do your own research on his diet because avian vets do not study parrot nutrition at all - and I do mean AT ALL! I have three avian medicine and surgery text books, the same kind the avian vets use to pass the exam that gives them the board certification and there is no parrot nutrition anything anywhere on them. There is a VERY small and vague chapter on avian nutrition but, when you take into consideration that there are birds which eat meat, birds which eat fish, birds that eat seeds, birds that eat nectar, birds that eat insects and birds that eat everything, it makes sense because if the text book actually covered every single avian dietary ecology, it would look like the English Encyclopedia set
And I will share something with you, the fact that avian vets who have not had multiple parrots for years give advice on diet is a beef of mine with them because I really do not think that anybody who has no knowledge of a subject as important as diet is to an undomesticated animal should be giving their uninformed opinion on it. And I will tell you one more thing, 2 of my avian vets [they both kept multiple parrots of their own] told me that they recommended pellets not because they thought it was the best dietary option for parrots but because it was the lesser evil compared to an all seed diet. But I happen to think that bird keepers deserve the benefit of the doubt and should be taught to feed their birds the right kind of food - and, to a GCC this means low protein [pellets are too high], high moisture [pellets are WAAAAAYYY too dry], low fat [this is OK in pellets] and high fiber [not OK in pellets because they don't use the right kind of fiber -there is a study done with African Grays].
Seeds are fine for parrots. It's what they eat in the wild. BUT you can't free or over feed them and they need to be the right kind of seed. For a GCC, one tablespoon of budgie seed for dinner is perfect with gloop [or mash or chop] and raw produce [with emphasis on large portions of fruit] for breakfast and all day eating. The gloop provides the high fiber and high moisture, the raw produce provides the phytonutrients, vitamins and minerals and the budgie seed mix is low protein and low fat.
Now, if you choose not to change his diet, it's your decision but, please, reconsider giving him extra vitamins/minerals on top of the pellets which are already fortified with them because too much is as bad as too little and, in fact, it kills them faster.