I am sorry but mushy food does NOT make them regurgitate. Regurgitation by a single bird (meaning not one that is paired to another and it's feeding its mate or the babies during breeding season which is perfectly normal) ALWAYS means overly hormonal. Period. But it's not mushy food that does it (this is something we used to believe years ago when we did not know enough about them), it's the wrong light schedule (research avian photoperiodism, avian endocrine system and avian reproductive system) and the wrong diet that does it. ALL my birds (and I have a lot of them now and had around 240 in my rescue, including the ekkies that did not regurgitate, either) eat mushy food every single day of their lives and they are not overly hormonal. They get hormonal ONLY during breeding season but even then, none of my single birds and most of my paired ones don't even regurgitate because I don't give them nests. Birds hormonal production triggers are strictly environmental: daylight length, weather and diet but, when we say diet, we mean protein content and not whether the food itself is hard or soft or mushy or whatever.
Nutriberries are seeds and they are not good for ekkies. Like I said, do not take an avian vet's opinion on diet or behavior, they do not study these subjects - they study biology, anatomy, physiology, pathogens, diseases and medicines. That's it. So, if the bird is sick or injured, they are the best person for it but, when it comes to husbandry (diet, light, housing, behavior, etc), they know as much as anybody else who has not studied the subjects.
Don't take anybody's word for anything - not even mine! Do your own research and you will see.
I am attaching links to avian medicine texts so you can see for yourself that avian vets do NOT study parrots' nutrition, dietary ecology or behavior:
https://www.melbhattan.com/handbook-of-avian-medicine/http://avianmedicine.net/wp/publication ... -medicine/