Rolling and drying leaves?! HELP

Alright well I've been having a problem with these babies since day one. First they got over nuted, burnt them a little but I flushed them out for a few days. Everything seemed to be recovering than the lower fan leaves started to curl and become brittle. (Also note that the damaged leaves seem to have a copperish tinge to them in spots)

They're under a 400watt hps at the moment, switched out the MH a few days ago.
Temp is always between 75-80F
Soil is one part peat moss, one part organic soil, and one part perlite.
I don't believe it's heat stress seeing as it seems to be starting from the lower leaves and moving up.

Please, any help would be fantastic!

Im at a loss for a solution, I am going to be transplanting them soon aswell.

Leaves curling up=heat stress, leaves curling down= ferts........usually. check all of your basics, ya know PPM, PH etc. Myself i'd scrap them and start over. If their seeds then their pretty stressed and your male/female ratio will suck. If their clones then your finally outcome will most likely be week..........

Pic #7 looks like just your oldest leaves are dying. Top looks decent......

If they were heat stressed it would be showing on the leaves closest to the light. Temps are always between 75 and 80.
I already thought I said that >.>

No, it keeps working its way up. Those leaves aren't that old, I keep pinching the dead ones off.

Any more suggestions?

Also Humidity sits at about 50%

How far away is ur 400 from the canopy?

It's aprox. 2feet from the top of the plant.