Im sorry you lost your baby! No idea what the white spot is, but I did lose one of my buff orpingtons at about a week old, had no idea why. Didnt seem to have anything wrong with her (with my limited knowledge I only looked for obvious signs such as trauma and pasty butt), just found her dead in the morning.
Still changed all bedding, feed, and water just in case (my 11 others are fine a month later). I was told by my chicken friends that there is a high mortality rate in chicks, and sometimes they just die for no reason that you can tell. Good luck with your other girls!
I just lost one at 6 weeks. She was walking around, then sat down, rolled to her side and was dead. I was sitting out in the brooder at the time and watched it, nobody was picking on her, nature just took over. No idea on the white spot, just chalk it up to nature and move on.