Growth is dependent on so many factors.
But I believe one of the most important are water changes.
I had grammodes go from 1" juvies from an ACA convention, to about 7" in less than a year.
I believe if I had done maybe one 40% water change per week, growth would have been much slower.
But I do a 30-40% water change every other day.
And if a tank is small, (under 100 gallons) it may need even more water changes, because concentration of nutrients like nitrate builds up so much faster.
I see posts all the time about supposed slow growing species, but in my case, I find the reason, is often about other factors.