Greetings, fellow grower! Everything was going good up to the point your unused nutrients started to accumulate in the soil. Do you have an EC pen? The fix is to do a heavy watering done with a slow trickle, and let it keep trickling and periodically collecting and checking the water running out until the pen reads no higher than 1250 ppm or 2.5 EC. Work slowly and in increments so you don't overshoot your target and bottom out the EC and displace too much microbial life. The leaves aren't going to fix themselves, but we want to stop the burn from reaching all the way to the bud and it's already knocking at the door of your sugars, yo you want to act immediately and not put it off. I'd be curious to know what that EC number will climb to but I have a feeling it could go to 3.5-4.0 before you see it start coming down based on the plant's appearance. This is one that gets many of us off guard, and sometimes we don't catch on until after a couple years how much water volume you want to be working with. I've been doing this a few years now and I still rely on a pen to give me a rough idea of what's going on in the soil. I don't trust pH pens though. Too prone to losing calibration. Drops are always reliable.