Day 32 after germination, 15 days under the metal halide...
Well, I've come to the conclusion that I was so worried about overwatering, and ended up UNDERwatering. I ran 2.5 gallons over all the plants last watering, and they took off really fast.
I just let them almost completely dry out, and this time today I ran 3 gallons over them.
I removed 6 plants, so now im at 32. All 6 had purple stalks and stems, their lower leaves were yellow, and even dying (see pics). Obvious nutrient burn (lucky it wasn't bad though). I read tons of threads about purple stems, and since its not genetic (all other plants are green), I am going to guess underwatering could be it. I never watered until runoff. So I likely just kept watering the surface over and over while the lower parts of the pots remained dry.
I suspected that the jiffy pots were restricting root growth earlier on, and so I had a look of the roots of the plants I was throwing away. Those jiffy pots have a small hole in the bottom center, and that's about the only place that roots were coming from. They weren't hardly breaking through the sides of the jiffy pots. (see pics). So my conclusion, and what i've learned in the past couple weeks is...
1. always water until there is runoff
2. don't worry so much about giving nutes. and start at 1/4 strength, not 1/2
3. never ever use jiffy pots.