Northern light auto sensi seeds 1° grow

Everything was good until the last day of this week , the plant seem a bit sad but I didn't see any signs of nutrients deficit or sunburn so I flushed with 2 Lt of 6.5 pH water with no nutrients and immediately bounced back to normal , so I think it was a pH problem or too many salts in the soil . I'll give her another simple watering and reduce the quantity of feeding for the next week's .