DE can be dangerous to breathe and irritating to eyes. I would get a proper medicine such as Valbazen or SafeGuard Liquid Goat Wormer that is proven to treat worms safely, and toss the DE. Respiratory diseases can cause sneezing, watery eyes, nasal drainage, gasping, head shaking, and noisy breathing. There are several common ones. Sneezing during feeding or when there is poor ventlation or dust, can be normal. I have seen infectious bronchitis before, and the chickens may sneeze every few minutes, and it can last about a month, eventually running it's course over time. Some observation of when they are sneezing and other symptoms, can help determine if you are seeing an illness or just irritation.
