There is nothing wrong with that kind of growth. It's almost impossible to answer this question with any specific linear dimension. In general, cichlids...and more than likely MOST fish...will grow quicker from birth to small fry. It 's carved into their genetic code to get big quick or be eaten. Once they hit a certain size, the growing slows down with growth spurts common. So it depend on where on the "life cycle" your fish is now.
I have a half dozen Managuense that grew up in three different tanks. Four are about the same age. There is a marked difference in the size of the male in the SMALLER tank. (100 gallon) As opposed to the ones in the pond. Smaller tank, smaller size in this case. Big water grows bigger fish.
The Managuense I have (Jumbo) seemed like he was two inches forever, then just started growing. As a fry he grew at approximately 1/4 inch a month in total length. But at the same time appeared thicker and higher bodied. How do you factor that into "how big in how long?" Impossible.
So you go from this:
to this...
then this...
What you find out is that one or another are bigger. In this case the larger fry in the tank is "Jumbo" here at a little over a year...
And here seven or so years later.
I think that part of what you have to look at is the percentage of their body mass it increased. From wiggler to an inch over any time period is an impressive figure if you consider how much it's grown in mass.
And among fish of the same breed and in fact, brood, some grow faster than others as noted in the photo. I can't back it up, but I would beleive that tank raised specimes from fish well estbablished over the years would have fry that wouldn't grow as fast with a pair of wild fish. Again, just a guess, but I would think that the predation factor weighs heavily on growth..and that the farther away you get from having it imbedded in your behaviour the less danger and the speed of growth would not be as necessary.
The best piece of advice I ever received for the growth of fish was from Wayne Leibel, who said in a seminar that water changes were more important for overall growth. Good luck. Great fish.