Problem with the hatch

Had 1000 NBW eggs in the hatcher. The first wave of about 50% hatched on time. Waited almost 48 hrs. after the hatch to remove the chicks. Sprayed the remaining eggs with warm water and waited. Round 2 started well and just seamed to stop. About 100 more hatched and another 300 were already pipped. Most of those almost out and then nothing more. Have gone thru the our posts but haven't found anything helpful. Temp stayed @ 98.5 and wet blub @ 90. There were even dead chicks in the trays. Could it be a contamination problem? I don't think the power was off for several hrs. during the night because I didn't have any blinking digital clocks. Tell me what I did wrong this time.