It depends a lot on a lot of different factors. Temperature, food, water quality, space, crowding and probably other things will determine growht rates.
More food and higher protein content will lead to faster growth. Higher temps will do the same. 5 fish in a 10 gallon will grow faster than 20. But remember, quality offspring grow slowly so be patient. If you really want high quality show specimens you will need to feed them a quality mixed diet of the proper foods and keep them at a temperature close to the normal one they would find in nature, I think it is 76-78F but don't quote me on that.