Haha! Don't feel bad... a lot of us have taken that same path!
I have given him some small cuts of Prawns and Cichlid Excel pallets that has Contains pure-cultured Spirulina.
Vegetarian fish , big cuts of flesh is not ideal at this infant stage , add Veggie material , broccoli florets simmered and green shtuff pellet wafers
Giraffe cats eat spirulina / algae pellets and plant matter. They don't eat massivore or sinking carnivore pellets. That's why your growth rate has been slow.