Its about 3 weeks old. It been very light green since it sprouted. The oldest leaves started to turn yellow, and eventually brown. They are not very crispy, and don't crumble much when you touch them. Stems are slightly purple. I am watering with 7.4+ and the runoff is slightly below 6. It was recently transplanted into different soil. Does this look like low PH? I doubt it's over watering because it happened while I was on vacation and the soil was bone dry.