To be honest it's a classic scenario, having a number of juveniles that will overstock a tank once they near adult size, but wanting to "fill up" the tank in the meantime. I won't say it's a mistake, necessarily, because another scenario is you know what you have, the 125 is just your grow out tank, and some fish will be moved to other tanks, traded later on, etc.
Everything's a matter of scale and what I often do when I have small juveniles in a tank I plan to keep them in long term is enjoy the phase where that scale is something a bit closer to nature vs. simply being an adequate tank. If you see the tank that way there's not necessarily a need to add fish, if that makes sense, though, again, if you choose to have more juveniles than what adults the tank will eventually hold, realize it's a temporary option.