I had a total of 14 chicks. I sold 5 of them. About 2 days later I was contacted by the buyer saying 2 of the 5 were sick. Then again a couple days later I was contacted saying that a couple more had started to show sign. None of the other chicks that I still have are showing any illness. In not sure how to respond. I've never had anyone contact me saying this before. Any suggestions?