hi there Rainbox, sorry but i have to disagree with my growmie roberts on this one. You can tell it's not a nutrient deficiency because of the discoloration and slight burnt tips on the leafs , this is always a nutrient excess, and by the way it has nothing to do with the spots you're referring to. what you're seeing is a magnesium deficiency due to the heavy light schedule you're under. you need to add cal mag (even in soil) if you have a heavy light schedule like what you have. if you add calmag the problem will stop spreading almost immediately and the plant should recover in about 10 days or so. Hope this helps ! 🚀