Click on the link provided by KikisGirls. Someone had birds with the same symptoms and determined that it was the result of water deprivation because of a nipple system. In many instances small chicks are unable to activate a nipple system.
You mention that you have recently switched to a nipple watering system. Is there any possibility that these chicks are not able to access water now ? Symptoms that you describe can also be caused by dehydration. Water deprived chicks will also over drink and drool when supplied with readily...