whats wrong at the Gun fight? Spider mites? stress? Disease?

Ill start by telling you this is my first grow i have a 1.5 x 3ft box with 630w cfl i did have about 50-60 bag seeds growing in my cooking pan. now im down to 40-50 my plan is for a small compact SOG with what ever ladys show up. they are a little over 10days old now. i topped the majority of them 2 days ago, yesterday i noticed what looked like spider mites. So i went to stauffers of kissel hill nursery to get some supplys to kill the bastards. I cut some leaves off and showed the growing specialist there and he said he thought it was disease not spider mites and to just cut the dead areas off give it some water and plenty of light so i did and today i woke up to more of this stuff. so i just pulled all the affected plants out about 7. and took pics to ask you guys the true experts what you think it is.

any body have any ideas what is wrong?

look under the leaves with magnifying glass and see if you can see any tiny bugs........doubt you will see by eye

I did do that and i didnt see anything any other ideas,