did you open up all of your unhatched eggs? You may have had a few more if you didn't and not known it. I can't remember what the odds are of the recessive white in the BCM but it is I think 25% chicks should hatch white and I believe it goes by number of matings, not number of eggs laid as one mating can create fertile eggs for up to 21 days. If your hen that has the recessive white gene (if she does.....) is not the cocks favorite, he may not mate her very often and that would help explain the low percentage.
No I haven't opened the unhatched eggs.
When I put the eggs in the Brinsea, I get an 80-90% hatch.
If I don't have room in the Brinsea, I put them in a styro and I only get about a 50% hatch.