I candled the first time on Sunday night (I had set the previous Monday night). Of the 16 eggs set, I saw development in 12 eggs, two eggs I could not tell (difficult to see through the shell, but I think I saw veins), and two eggs had faint blood rings. One egg with the faint blood ring was the one you mentioned might be from the Splash Rock, and the other egg was very similar to it (maybe from the same hen). I am excited.
As far as females growing feathers down the back before males, that is how I tend to determine gender in the BBS LF Cochins we have. They mature painfully slow, and comb size is not a good indicator until after 6 weeks (more like week 8 and later). I can sometimes go by which chicks start to feather on the shoulders first.