Tips burning, plants dying, very fast progression

I had extremely similar looking issue during the late stages of flowering in my last/first indoor batch. This leaves literally looked identical to your pictures. In the end, I believe my problem was due to a very high TDS/EC in my local water supply. Though I had been trying to manage PH in my nutrient mix, I had not monitored TDS at all and I'm sure the TDS/EC was off the charts (first timer). This was causing nutrients to get locked out as the flowering stage demanded more and more of them. I never got it resolved and that batch was dramatically reduced in output and size. My new batch is in buffered coco coir and pearlite, I'm using filtered water, and I'm measuring TDS/EC and PH very carefully both going into the plants and coming out at the bottom. If this is actually your problem, I suggest trying a complete flush with a flushing solution to break down the salts. Then start nutrients again with filtered water and carefully monitor the TDS/EC and PH on the front and back ends. Good luck!