Okay bought 8 new silkie chicks last Thursday. Some were close to a week and some 2 days old and in between. All did great for the first four days then they started dying. They all looked fine eating drinking running around the brooder. I have lost 6 of the 8 and have no clue why they were active and seemed healthy. It was a sudden thing too one minute great next lethargic and near death. Any thoughts?