With 40% RH and 30 degrees C it makes about 2.55 VPD (Vapour Pressure Deficit) that is high stress for plant. High temps with high PPM make the plant to consume more nutrients because it's using much more water for evaporation. Lowering PPM of solution will help. As I mentioned in my comment earlier, the plant likely has nutrient burn due to very high ppm is applied once per week. It's better to lower feeding for some time and then feed every other watering (feeding-watering-feeding-watering). Also apply relevant PPM according to temperature. High temperatures require less PPM. That's my IMHO.