They're out of the same package of seeds, or did you save some kernels from last years plants??

I'm don't have a lot of expertise with corn, but I've heard it said that sunlight is critical to good corn flavor. You might have just had a season with less sunlight.

If other corn is nearby - especially field corn - some degree of cross pollination may have occurred. Unlike most vegetables, which show no effects from crossing until that seed is planted, corn crosses may have an immediate impact on flavor & texture.

Actually, only the individual grains that are crossed will be affected...and they will be very dark orange and you can't miss them.

I used seeds from the same packet and there is no other corn even remotely close enough to cross pollinate.