Athosanswered grow question 6 years ago There's quite a bit of information missing. Let's start by what you are telling us (and showing us). Watering: half a gallon a day? really ? that's way too much, I hope that's a misunderstanding and you just entered the information wrong. In the previous weeks there were clear signs of nutrient excess (really dark leaves) and nute burn (burnt tips). The issue is on the upper leaves and it doesn't look like calcium deficiency (which as an inmobile elemente does affect upper leaves). Since you don't post pH, I can only assume you are not meassuring it (nor adjusting it), this can lead to many phantom deficiencies and / or werid leaf issues (like yours). Second, it might be Potassium toxicity, but it does not look quite exactly like that. Third, if the watering data is correct, then you are overwatering and you might have fungus gnat damage. Fourth, it could also be some kind of fungus, (it does look like septoria). Anyway this is what I would do: (i) Check pH (and adjust future watering / feedings); (ii) check feeding strength with an Ec / PPM meter; (iii) let the soil dry before giving more water and check for fungus gnat larvae presence; (iv) remove affected leaves and apply mulch and / or sand on top of soil since both gnats and fungus spread through it; (v) increase air circulation and exhaust. Hope that helps