I have 5 bantum brahma chicks. Yesterday they all had a lot of poop build up on their bottoms. I gave them baths and brought them inside so I could watch them closer (they were in the shop). Today 1 of them had a lot of poop built up on her bottoms again, so another bath. My question is why would they have so much poop building up on their bottoms, Is there something going on causing this? My 6 week olds didn't have this problem, they are standard size pullets. Any help or advice would be appreciated. Here's what they are getting: Chick Starter, water with a bit of apple cider vinegar, they are in a large box with pine shavings and a heat lamp, keeping the area at about 88-90 F. I tried to give them yogurt (plain greek) yesterday, they weren't interested in it, other than walking through the bowl.