it's a bit hard to tell from your pics as when I click on them they are so huge they are a bit out of focus. I'm not sure but could it be salt injury caused by too much fert? the soil in the first pics looks like it has a whitish deposit on it and excess fertiliser will give a burnt look. if your fert regime is not excessive, was there something planted in this spot before as there looks to be root residue present?
there is some blackening of the leaf veins also, this could be due to herbicide injury, have you been spraying poisons recently?