Nutrient Film Technique?
thats advanced level shit, theres so much that can go wrong...
you could have bacterial growth in your tubes, your water channels could be filled with algae, your pump may not be moving enough water, your roots may be stacking upo on top of each other and drying out, you may have light leaks that are killing your roots, your solution may not be 5.8-6.0 at all, unless youre testing it you cant be sure.
go over your whole system bit by bit, make sure you have no light leaks, no algae buildup, no dead roots, no funky smells, and definitely make sure your solution is as close to 7.0 as you can get it.
those pics are screaming root stress, and when you take pics, do it in NORMAL light not HID lights.
if we cant see the actual color of your leafs we cant tell whats going on.
looks like you may have an overabundance of nitrogen though, cuz them leafs is dark.