The yellow poop for the first few days is normal. First poop will be black then the next ones will be yellow. It just means they are getting mom's milk. It takes a few days before they start to form pellets. If the boy seems constipated, make sure his booty is clean. The yellow poop is like goat super glue and can stick to their backsides and keep them from being able to poop. If he has a clean booty, you might consider giving him an enema using a small syringe and warm water. The diarrhea is concerning. How much are you feeding them?