Reporting
It may be a pollination
It may be a pollination issue. Corn grows best in a block system--four short rows instead of long individual rows--as the pollen (which is carried by wind) can better reach the silk to fill out the ears. At this stage, you could try hand pollinating by rubbing the tassles on the new silk. Also, corn is a heavy feeder and drinker. Side dress your crop with a high-nitrogen fertilizer.