My chickens that are approximately 8 weeks old are getting sick and dying. I've had 5 die in the last 5 days. I have approx. 60 chickens..25 are very healthy free range chickens; 23 three week old chicks that seem to be very healthy as well; and started with 15 other chicks (now about 8 weeks old); however, 5 have died for no apparent reasons. All of my small chicks are in large cages to protect them from the large chickens. I clean all feeders & waterers daily, as well as clean their coop on a regular basis during this wet season. There are no obvious reasons as to why the chicks are getting sick; they discountinue eating/drinking and become very weak then die after 24 hours. Any suggestions from anyone??