Things to look for in chicks would be excessive sleepiness, lethergic behavior, puffed up or ruffled feathers, foamy or/and runny poo, poo with small amounts of blood in it. ( the bloody poo does not always have to be present to be sick) These symptoms describe a life threatening illness called coccidosis that young chicks can be susceptible too. if coccidosis is suspected treat ALL chicks with a medication called Amprolium. it's always good to have a fresh bottle on hand when raising chicks. The brand name for Amprolium depends on where you live. In my area it's called CORID. it's added to the drinking water. you should be able to go into any feed store and ask for Amprolium and they usually have it in stock. Coccidosis is a large cause of chick death. ...In your brooder do your chicks have a warm side and a COOL side where they can regulate there temperature? Are you checking the warm side temperature with a Thermometer? Are you dropping the temperature each week of life by 5 degrees? This is done each week until room temperature is reached and heat is no longer needed. Over heating can be as dangerous for chicks as chilling. in fact overheating causes pasting on their bottoms. Do you check there bottoms and make sure there vent is clean and able to pass poop? pasty bottom can also kill because the chick can not eliminate waste. I'm sure you likely know these things already but you asked what could be happening to your chicks so I'm trying to give a few things that might cause death. I'm very very sorry for your losses and do hope this helps a bit. These are some major things I can think of. I wish you the best.
