Your complete watering procedure is a problem the way I see it. If you are splitting a gallon of water between 6 plants, the roots are not even getting wet. You have your plants in 5-gallon buckets. With that little water, your roots are not even getting wet when you water. Like I said, soak the soil when you water, then let it dry out. In a 5-gallon bucket, I would imagine you would need at least a gallon of water per bucket. You want to see a little water come out the bottom of the bucket to know that you have soaked the soil. Your roots will be a lot happier.