I think the N OD is a secondary problem. Hold off N in flower ANYWAY.

Don't lie the whole pot on its side, come on, think about the logic in that- bend the plant gently away from the lights.

IMHO= in my humble opinion and I don't know where you got 'combustion' from, you aren't to that step yet.

Nice phrasing by the way; it's like an ambient poem about sick plants...

When a plant is root-bound, all the flushing and pH adjustment in the world is, at best, a temporary fix.

COLD WET SOIL KILLS PLANTS. When you have ANY nutrient or pH imbalance, and you will continue to have them until you re-pot, cold soil will make it many-fold worse.

You HAVE to repot and you HAVE to lift off the cold ground.

You may or may not choose to take this advice; it sounds like you're not going to, so I can't help any more here. I'm not going to sulk and pout over having wasted my time, but I know how to grow plants. Ignore this advice at your own plants' peril.