I'm on my first grow, so take my notes as a help and not as a true diagnosis.
Have you been spraying your plants with water or else? You seem to have light burn from water/nutes droplets. I had that on my plants as well, I went ahead and upped my nutes(Sensi Bloom & Cal-Mag) and with that caused a nutrient burn followed by a nutrient lockout. Which then got me so confused, I had to flush my plants, and they seem to be happier now. You also said to have lowered your lights recently, that adds to my suspicion, if you are spraying consider doing it less or wipe off some of the big droplets that stay on the leafs.