Dwarf boa(cay caulker) Size Difference

hello all, im seeking some knowledge from people with more experience then i do at the moment.
not that its a problem, just a questions that i would like to have it answered for my curiosity and future references.
any advise or input would be greatly appreciated.

before i get into anything i do wanna say first, i luv em! they look amazing and very well taken care of, huge thx to breeders whom let me get this beautiful animals if they happen to recognize me on here.
so here it goes....

i recently acquired 3 cay caulker boas.
2013 cay caulker female. 146 gram 10/13/17 approx.

2016 cay caulker male. 191 gram 10/17/17 approx.
2016 cay caulker female. 320 gram 10/17/17 approx.

got the 2013 female as single, and 16's as a pair from two different breeders.
weights are basically recorded on the date i received em if not day after.
far as what i learned from numerous source of info's. generally females will hit full maturity for breeding at 4-5 years since they are really small feeders and slow growers.

so my question is...
as you guys can see by weight of them, my year old female is pretty much twice of size as to 4 year old female. 16's female is not twice longer then 13's female but significantly longer and thicker.
since 2013 female is 4 years old, she should be right at her full maturity but so small when compared.
could there be such a difference in size even in same species?
im also under a impression that they have very small gene pool, which means they can't be too differ from one a another, only makes harder for me to understand what could be the factor for such an growth/size difference.
i do not doubt their integrity of a blood or purity as of dwarfs, since i got them from reputable breeders.
just wondering if this was common things to happen.
if i were to say ex:
one female BRB from one clutch hitting 4ft mark on its first year,
while another female BRB from different clutch hitting only 2ft mark on its first year when fed identically.

previous owner/breeder of 2016's did told me their mother was a big girl considering when its a dwarf species ( 5- 5.5ft)

thank you,

16's female is rivaling size with my 6mo' Suriname boa which dosent mean anything but i still find it to be pretty cool lol.