First Plant...Need some help

Hey guys. This is my first time growing. I had to leave my apartment for thanksgiving break. I was gone 5 days. When i came back my plant was bigger, but yellow with burns. I narrowed it down to a severe nitrogen deficiency, combined with a little nut burn(must have splashed the leaves). That was a week ago, I stepped my act up a bit since then. I bought a Ph tester...the ph is around 6.2-6.3. I'm using miracle grow 30-10-10 its about 75% strength of the recommendation on the package. I'm growing hydroponic ally, its my own version of a water culture(growing in a fish tank). The lighting is a 400W Mh light about 24 inches away form the top of the plant. Now the 3 point fan leaves that were yellow are starting to get greener, but the second set of leaves looked wilted from heat....I raised the lights and put in another fan i think that did it. Now, another set of leaves are growing in they look alright but I'm curious if I'm doing everything the right way. Any feedback would be great. For some reason the site wouldn't let me post a pic so if you look up the title in indoor growing i posted it there as well with 4 pics.

Welcome to the forum. Gee, less than 20 minutes to post it twice on a Saturday night. Ummm... maybe everyone was busy. How old is that plant??

Thanks, the plant is between 2-3 weeks old, the pictures were taken yesterday though. So what do ya think about the plant.