We've had 3 black rock hens for about 6 weeks. They are about 6 months old. They have access to a large garden, and we've fed them a mixture of ad lib pellets, veggies, grain etc. They are all laying and feeding well and seem very perky. However one of them has diarrhea (brown and runny), and consequently a messy bottom. We've been advised to only feed them the pellets, but we can't stop them foraging, even if we don't feed them any veggies etc. Would they eat things that are bad for them? Should we wash the poo-y bottom? Any likely causes/solutions?