I have just had a look a my corn plants as some look rather brown and reddish colour. I have done a few searches apparently they were due to not enough watering, too much direct sunlight or not the right soil. I am growing them by the fence on the borders. I am growing Fiesta and Mirrai Picnic F1 variety in the garden. I have harvested them today, one look poorly/unripe, two look unripe and one looking all right. Last year I had none ripen as they tend to take long time to ripen in London’s climate. Hopefully it will be better luck for me next year.