On Oct 30 I bought 12 new chicks from the feed store. The were fine and growng well. I went away for 5 days and left a friend to care for and feed them. I returned to find 2 dead. I have them in about 30 by 30 by 36 inch high cage. I had been putting in fresh water and newspaper every other day. I don't think my friend ever changed the paper, because the cage was very dirty when i returned. One of them looks sick now. What could have caused the problem? Besides cleaning, what else should i do to care of the rest of my chicks?