How warm is your brooder temperature? Make sure that it is 90 degrees for the first week with a cooler spot to escape to. Use a thermometer on the floor in the warmest spot. Pasty butt can be common and a sign of dehydration. Make sure that the chick is drinking well, and adding electolytes such as SaveAChick or a 1/4 tsp of sugar to a cup of tepid water. Dip it's beak often, and make sure it isn't overheated.