light is not going to cause that problem.

checkout my thread in this forum titled Spent $4000.
my water is high in calcite as i mentioned. this combines with the P nute to form calcium phosphate thus making the P immobile. lack of P causes exactly what i described: curling and contorting with dark splotches.
you may not have the same hardwater that i have, but you surely have a nute problem. General Hydro's bloom is 0-5-4 NPK because the need for phosphorous is great during flowering.

wade your way through the advice here and try to establish a few that you trust their advice. i personally usually refer to my source, which is often "Indoor Marijuana Horticulture", an amazing resource.