I'm not a breeder or have much info to back this up but I do have a few theories below if you want to hear them. I've been doing a lot of research lately and I'll continue to do so for a few months at least, but here are some thoughts.... oh and I started writing the bottom part first then decided I didn't want to say to much just to stick my foot in my mouth later so I added this as a prequil of sorts.

I think perhaps some of the reason you were having a little trouble getting help with this is because your post is a little jumbled and difficult to read in some spots. Have they shed yet? if not perhaps the meals they had were a little smaller than the ones their brothers and sisters ate causing them to grow just a little slower. Have you weighed them out to see if maybe they just haven't grown as much as the others? After all they will shed when their skin becomes tight and uncomfortable. Until then just keep an eye out.