I have raised many clutches of veilds, years ago, before good info was around. All I did was feed rep-cal dusted crickets to them. No UVB, No sunlight, etc... I never had any MBD--any.
All of my veilds grew stedily for 2-3 months. At this time, they'd grow really really fast for about 6-8 months, then level off a bit. They did NOT reach their full size( 13-15 inches) until they were about 15 months old. Now, you might say 15 inches is small, well it is. My line of veilds were from WC parents, and the father was 12" long, but had unibaginably bright coloration. None of his babies grew more than 15" long(the father of one of the females I bred him with was about 16"
Some veilds WILL NOT get big. Most stay around 15", some get quite a bit bigger, there are some in the wild that are greater than(yes LONGER THAN) two feet--I have seen some of these 25 inchers a few years back--what monsters, they're the size of melleri.
My current veild is about 18", a pretty big boy. It too him about 15 months to get that big, and he was around a foot at a year old. When he was 3 months old, he was eating 1/4 inch crickets.
The current 3 month old I have are eating 1/2 inch crickets, and COULD easily eat adults. They are HUGE.
they also have MBD. With these I used gutloads, reptisun UVB bulbs, and rep-cal. Still, they developed MBD. I don't know FOR SURE why they have it--I definatly gave them "better" care than my others(in that they got UVB).
the only thing I can think of is that they were growing too fast. They could have started off so fast, that their bones were unable to ossify fast enough. This seems to be what has happened, as the bends in their arms and legs are right at where the growth plates would be.
Another possible contributor to this could be the fact that they were raised in pure sunlight. Possibly, once exposd to sunlight, they are unable to process D3 in it's pure form enough to allow for proper growth.
If you can get them to grow fast without any health problems, then they are probably growing at a natural rate. However, if you feed them as much as they can eat, several tiems a day, they will grow faster than they would in any natural state. They have not evolved to cope with such abundant food, and might develop health problems(fatty livers, bone deformities, edema,e tc.)
I have not seen a chameleon become stunted unless it was starved. a healthy, well maintained chameleon will grow up slower if fed less, but it will still grow up. If fed too much, you can have the opposite problems, jsut like people that grow abnormally fast(because of gigantisim), they will develop joint and bone problems, as their skeleton will not be able to support such a rapidly growing body.