Quote: Yes. Recently there's been some kind of outbreak of mysteriously stunted chicks who simply aren't developing. I think it may be an inherited endocrinal disorder; if large scale breeders and hatcheries are not seeing the chicks they hatch make it to adulthood they may find it difficult to know for sure what they're breeding. I really don't believe in using a computer to assign breeders to one another, nor do I think it's wise to not keep a sample of the results until at least three years old to see what's being bred. Just a theory and my two cent's worth, combined.
However in your case it is more likely an environmental or symptomatic 'development disorder' --- almost any illness, injury or over/under-nutritive occurrence can set them back, produce inferior adults, and delay or prevent full growth.
People on this thread have already supplied the most common causes of pale crests but in general it can be considered a reliable sign of suppressed vitality; broodies are in a low-consumption semi-suspension state so their crests tend to pale; since bright red crests are a sign of sexual maturity, I think a paler broody's crest helps to let the rooster know (if he's the thick skulled sort) that she's not 'up for it' --- her body is not advertising reproductive availability while pale.
If crests go pale under stress they are either in shock or have weak cardiovascular systems. A rooster who lived a really healthy life will often maintain a bright red crest and wattles even after death from even long-running injury and infection. If you have many pale birds I would suggest making sure the worm and other parasite burdens are controlled, and supplying the means to strong health. The ways I personally achieve this are to give raw minced garlic as a staple food (average of a clove per bird, per day) and a pinch of granulated or powdered kelp (per bird, per day, average). Kelp will regulate their endocrinal systems and is a carminative, meaning (more or less) it'll redden them up. Another thing: if you think your animals are breeding true to type or are good purebred specimens, you will never know unless they are having kelp. It will allow full visual expression of what the bird's true phenotype is. 'Complete' feeds from produce stores can't match it unless they too have kelp and haven't cooked it to within an inch of its life.
Best wishes to you and yours.