The sneezing sounded like a respiratory problem. Gasping can be the same, but also common when dying. So sorry that you are losing them. Buying chicks from others can always be a gamble. After I have read a lot about hatching eggs, a lot of the condition of chicks depends on the health and good condition of the parent stock, the vigor of the particular breed, how clean the incubator or nest was, and the condition of the eggs. So many different problems can affect young chicks from shipping problems to vitamin or mineral deficiency.