I have a female veiled who is almost a year old, and she is as big as a 6 month old. She is very healthy, no MBD or anything, she is just small. As long as they dont have any health conditions, their size doesn't matter too much. I am pretty sure that small chameleons always go through a growth spurt at one point or another. My little girl is in a growth spurt right now and I am noticing her size difference now.