I got 4 chicks last Weds from MPC, two Orpintons and 2 Silkies. This is my first flock. They have been doing great. This morning I cleaned out their bedding for the second time. I don't do anything but change out the soiled bedding for clean. I use the same pine shavings each time. They've been eating great and drinking great. I monitor them closely, checking on them every couple of hours as one of my Silkies has had a pasty butt. I haven't noticed anything with this chick. She's been active, running around, drinking and eating. She was full of spunk as usual when I cleaned the brooder. I went back mabye 2 hours later and she was gone
She was in her normal sleeping position, so at first I just thought she was sleeping. They were given the Mareck's vaccine and I haven't had them outside yet. I have been feeding them Manna Pro chicken starter crumbles. The other girls seem fine, but now I'm worried for them since there was nothing obviously wrong with the poor girl who died. Any ideas on what could have happened? Is there something I should do to keep my others safe?
Thanks!

Thanks!