nobody mentioned temperature, but you're way too hot. 23-26*C is the sweet spot for canna. You are locking out minerals because your soil pH is likely way off at that temperature....I would suspect P based on the crisping/browning of leaves. Before I added/removed anything from the soil, I'd optimize your grow conditions. Cannabis is a weed, and given the right environment, it should be able to grow in a wide range of soil conditions. If you can get your grow room to 24*/50% humidity, then make sure your feed water is properly balanced, you can get this thing back on the rails fairly easily. I would try to flush the pot if you're getting wildly different water in/runoff readings.