Please Help! Noob here...

This is my first grow. The first three pics are of my most stressed plant. I had all of them ~5 inches from my T5 fixture (6 bulb, 4') when this one started burning. Most of the others are alright, showing only very small burns. I raised the fixture to 2' from the plants about 2 days ago but they seem to be burning a little still. Is this just a delayed reaction, or could there be something else doing this?

For reference, the last pic is of one of my others, though all of them have been under the same conditions.

Temp: 80-85 F
Humidity: 40-50%

I'm sure I'm neglecting to provide other vital information, but please help!

they look hungry....and angry...

Most of the full-on yellow parts look to be Potassium deficient. The leaves that have no actual yellow on them but are a lighter shade of green are either N deficient or are suffering from a pH problem. Check the pH of the soil itself first (not runoff). Feed them an all-around fertilizer mix with extra K, pH adjusted so the soil reads 6.5 after watering.

Feed them but do not over do it,start of on a low dose use advanced sensi grow,sensi bloom later

zinc and potassium def looks like

They're only 17 days old, is it safe to start giving them nutrients?

just read all this dude this will help in identifying the prob!!!

http://www.icmag.com/ic/showthread.php?t=11688

Plants start needing weak nutrients when the 3-bladed leaves begin to grow in. This is often when they are transplanted from seed starter mix to nutritious soil.

Thank you all for the replies. I'll start them on some diluted nutrients tonight.

They are mature enough to handle full strength fertilizer mixes, even if they weren't deficient.