im tending to agree with the nutrient problem tho pretty hard to tell with those pics, (or problem with nutrients in soil as you say you haven't fed them) unless your camera can make leaf tips change colour.
I wouldn't worry about the light too much, tho i would replace it when possible.
My first grow was under a 35watt floro warehouse fitting that seemed to put out as much light as the flashlight on my phone. . . still got me stoned (somehow).
P.s. my neck hurts, consider rotating photos in the future if you can.