Candling brown eggs can be difficult. I typically use a high power LED flashlight. Still, all you can see if a solid blob versus a floating yoke. Compare one of your freshly layed eggs. Take out any that look like the freshly layed egg.
I usually don't candle until day 10 or so. And since all of mine are dark eggs, I just let any that look viable go for the duration.
Take the eggs out of the turner on day 18 and adjust your humidity level.
Good luck with it.