First signs of burning from feeding too much or too often or both. It is not caused by your lights. Give just plain water for the next two irrigations then start back on nutrients, but dialled back slightly. Your plants need to use up what is already there before any new nutrients are given, otherwise the burning will progress. Some plants are more sensitive to nutrients and what may be written on the bottle is only general advice, not specific for every plant and in every situation. Autos generally need less feeding than photoperiod plants and nearly all fertilizers are designed for photoperiod plants. Cheers, Orgnoman.