i have 3 pure leghorns , 2 pure aseel ,2 black cochins large flow , 1cubalaya /aseel cross ,3 cubalaya / mutt cross
all are large or standard flow and they are fed on grains and kitchen leftovers and grown out grains....they are fast and are in a room at night and morning but in a cage in the after noon and evening and most of the time they free range in my balcony
Well your caring for them excellently, i have no clue what could be a factor in their growth. other than the climate. But i doubt that would cause them to stay small....