Could be genetic, I'm by no means an expert. When I feed this particular tank (Otohime C2) I can see that the larger more agressive feeders seem to be taking the large chunks and the little guys are busy scraping at the left over dust size particles. There are only about 5 big one left in this tank I just need to sit down and catch them to put them over into the larger bodied tank. Aside from genetics, you can still clearly see the second stripe on these guys. Most of them lost that stripe by around 3/4 of an inch, I'm still thinking it's a food / space issue retarding growth.
We need more opinions on this topic for sure.
Thanks Bud -- Kurt