Don't feel bad at all for feeding Higgins or Zupreem

There is so much vilification of dyed pellets that is unearned. Would I prefer if my Jardine's ate something else than Zupreem Fruity? Of course! But mostly because I don't like having only one pellet available to me in case of stock shortages, recalls, etc.
The best pellet is the one they will eat, do well on, and that is easy for you to obtain and afford.
"Best" is subjective, and at the end of the day we're at the mercy of what they will actually consume.
In my experience with picky eaters, Zupreem FruitBlend has always been the clear winner. Most of my birds then went to Zupreem Natural, and from there were more able to convert to other pellets. But, that's not strictly necessary either.
I've had the worst luck with Harrison's and TOPS.
As for everything else (veggies, fruits, etc), it comes down to just trying a lot. Parrots are naturally neophobic and don't trust new foods easily. That's a survival mechanism that suits them well in the jungle but not as well in our house. My birds are always the most happy to eat food they steal from my plate, so if you aren't already a healthy eater, now's as good a time as any to start
Also experiment with how it's served. My Hahns only liked frozen carrots that she could squish and suck the life out of like Bunnicula, while one of my Quakers only liked them in raw matchsticks. My Bourke's likes them raw or frozen but diced up fine in the food processor. My Jardine's wants a whole raw baby carrot.
My Petco green cheek would eat almost anything for what its worth

She was partial to Quinoa and berries.