Leaf question?

I have a White Widow clone and it's been about a month since the date on the clone 1/15.. so, my problem is the leaves are starting to droop. Especially the bottom 2 fans, and the leaves facing my 400watt HPS light are getting black or brown tips and curling up, the ridges also seem to be experiencing a burn.. which i think may be my nutrients. I'm awaiting my water meter right now so I can't give measurements, but what sounds like the main problem? They feel a bit dry to the touch so i've been really fine misting the grow room. And i've got a fan running.

--The light WAS 18" from the plant and i moved it back to 24" when I figured heat stress may be a problem.

http://i27.tinypic.com/23wnurp.jpg
http://i32.tinypic.com/2ijg1sl.jpg

My first grow, btw.

[edit] that leaf is torn because the poor thing grew towards the CFLs I had it under for the first few days and burned.

I dumped my old reservoir, my friend said yesterday that he was going to pour in some more nutes and I remembered he was worried about burning, so fresh tap is in there right now.

From the description I was expecting a LOT worse. That plant looks healthy, if a bit scorched. VERY slightly.
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Edges curling up is indicative of heat stress so raising the lights was agood move. Also, heat will make fertilizer burn more damaging to your plants.