I am with you, I am concerned there are problems in the breeding lines, especially with the hatchery stock.
My cream Legbar is not only half the size she should be as an adult, but she rarely lays - and when she does, it's not blue eggs (they are pink). So she is definitely a genetic oddity (and yes, I am POSITIVE she is 100% Legbar and not a cross with anything).
Recently she has started laying soft and broken eggs frequently, and I'm sure the cause isn't her diet. She's just a weirdo. I really want to keep Legbars but just haven't had good luck so far, so might try ordering direct from Greenfire or one of the other reputable breeders.