For 1" to 3", I would expect longer than a month. I would say you have at least 3 months for that much growth.
Keep your weekly water change schedule. What % do you change each week?
I would consider mixing up the food offered. NLS is great food, but I would not give it exclusively. I use a flake mix (omega one color max and ocean nutrition veggie) and pellet mix (NLS thera A, omega one color max, Hikari cichlid excel).