I'm growing my first batch of tomato plants hydroponically, and after several weeks of energetic growth, I'm starting to see yellowing on many of the leaves, especially those on the lower branches (photo below). Nutrient deficiency? Parasite? Non-green thumbs? Any advice would be much appreciated!
If it helps, I'm located in the topics, daytime temperatures are 32-37C (90-100F) with 90% humidity, and the plants get about 8 hours of direct sun per day.