I am raising my first flock. They are three weeks old and two of the three barre rocks got pasty butt the first week. My Easter Eager's and Rhode Island reds were unaffected. I they all came from the feed store and were a few days old. this showed up in the first week. One had it bad and was very stunted. As soon as I realized what it was, I cleaned it off and kept her vent clean with the water q tip and Vaseline as it reoccurred for a few days. Unfortunately she lost the down around her vent. At three weeks it hasn't grown back. She is thriving now, finally getting wing feathers , she eats drinks , is social and seems relaxed and lays down. She is also half the size of the others. I don't see her getting pecked and she is eating, drinking, and pooping normally. Should I be concerned and are there any other steps I should take? Thanks for the advice!