I had 4 of 12 with bad pasty butt and 2 with the beginning of it. All the little butts went under the faucet, in my hand, and washed with very warm water. Then blown dry, in my hand, so I could feel the temp on my skin. Just like I do for my adult silkies.
To prevent further pasty butt, I'm trying apple cider vinegar, organic, with the mother in it. 1 tbl. per quart of water. Yogurt, mixed with scrambled egg, so they will eat it. Ground oatmeal with the medicated chick feed. I've also raised the heat lamp to make it cooler. They are very comfortable 1 week olds, in the dining room at 83 degrees. PB has disappeared in 2 days.
I am using playground sand as bedding.