4/20 sprout, got some questions

ok, so i stuck this seed in the dirt on 4/18. It sprouted on 4/20 so i cannot let it die! I didnt germinate it because i was being lazy. Now its growing ok, but its growing soo slow. I have it in a nice grow area with a 500w bulb on it about 3" away. I just covered the lower part of the stalk with dirt, now the seed leaves are turning yellow. Is it a little early for those to start dieing? The plant is still extremly small, its a little over 3". Also the stem all the way up to the fan leaves is a purplish red, im not complaining but what does this mean?

I guess there's a lot of possibilities. Light, watering (over/under). pH, nutrients (over nuting), and type of soil, to name a few. The purple stem thing im not sure of, but I've had the same thing happen b4 w/o problems... possibly genetics. The slow growth id say more light... but thats w/o knowing what kind of lights your using. Flouros are pretty slow unless you get them really close.

Now the watering. I don't water the leaves, and IF I do its during lights off, so they don't burn from the water droplets on the leaves. pH is always a possibility and don't rule out over nuting. It's really easy to OVER due things especially on your first grow.

When there young I only use pHed tap water to prevent over nuting until they're about 4 sets of leaves and healthy looking. Then I use 1/4 str and move my way up. Oh and what kind of soil ru using? A lot of soils will have time release nutes. I recommend some good foxfarm soil, someone else may know a good alternative for foxfarm if you cant find any. Ummm, I may have forgot something, cause I rant a lot sometimes LOL. But I hope this helps some.