The varies information regarding LED's is very confusing because we have so many different claims about watts and equal to in the brand information. The lights this individual mentioned are not the common ones available on the big A. These are a pricey alternate that is described by the manufacturer in factual terms so the light puts out more lumens/light than most are use to seeing for the stuff on the Big A. I would be really surprised if you followed the directions for a nutrients and got any lock out in 1 or 2 feedings. Now yes if you hit them at like 10,000 PPM's you can probably get that effect but the original post said he feed at 70 percent so I doubt there is any Nutrient burn or lock out. This is a matter of the light being too close to the plant and having the watts too high. Give the plants about a week of food and water and you will see new healthy grow. Also take note of the spots that have been burned by the lights, the reason you want to note this is because they will slowly begin to die and the plant will take the movable nutrients out of the leaf and it will either be permanently damaged or it will completely die. You want to note the locations of the burned leaf's because they are going to be there until the end of the plants life and you do not want to take those leaf's into consideration when judging the plants overall health.
The higher end LED's are much more powerful than we realize.