So, those are pretty far gone, I see 2 options:
You might try flushing heavily with water, I would use RO, distilled, or maybe filtered tap water, I believe your 400ppm tap water is likely not going to help and may introduce a new issue. Let the plants go a couple/few days before any nutrients added to try and finish flowering. If the plants live through the flush, start with low strength flowering nutrient mix, maybe 1/2 strength or less for the first two feedings. Based on the latest pics, I don't believe this option is gonna go too well, the leaf damage is pretty heavy. There is a good chance that flushing and leaving with little to no nutrients will finish off the plants.
The other option is to harvest now, cut your losses, and start a new grow. I can see good distribution of trichomes in the pics, and the smoke may not be full strength, but should be worth something. You're working with organic soil and nutes, so no need to flush before doing this. In the new grow, when it is time to change over to flowering, make sure to heavily flush and let the plants go a few days with nothing but water before flowering. This is to to eat up as much nitrogen and other nutrients as possible before adding your flowering nutrients at a low strength and then building up to full strength over the first couple weeks of flowering.
Disclaimer: It has been a long time since I grew in soil, but I've had similar issues in changeover to flowering, so I'm just basing this on what I remember from 12 years ago. Good luck!