against chubby baby neck crease yuckies: probiotic powder!
Neither of my other children really had that problem but while they were big babies (9lbs12oz and 9lbs 3oz at birth) they were also long and not roly-poly like Sophie is. I always washed her creases in the morning and at night but that darn neck crease always got so red and I hate to say it: gross. It was cheesy and smelly and not very pleasant. I tried washing and drying it more often but that seemed to just irritate her. I tried cornstarch which we all know just feeds yeast so obviously that didn't work. Then I thought I'd try some of the probiotic powder that I had in the freezer (Reuteri brand) and it honestly cleared it up almost completely overnight. It was completely gone by day 2! Just sprinkle a little bit on and wash it off in the morning.
Works like magic!