You've definitely got yourself into a jam and the clocks ticking. Burned before yes, can see. Now, she looks hungry to me. Understandably you've become nutrient shy now and the next wrong move will nullify this grow. You'll have no time to recover. What I would do, if you were to give me that plant and I wanted to nurse it back to health quickly. Cause if you do it right, she can recover. I would not over think things. I would use distilled water. Distilled water does not need to be PH checked, it is perfectly neutral and whatever the mediums PH is you are adding it to, it will become that PH. Healthy PH soil and distilled all the time = simplicity. Simplicity makes taking a wrong turn less likely. I would water her with distilled water and Black Strap Molasses (SULFUR FREE) at the rate of a teaspoon per quart. You can not use to much of this stuff. It feeds the soil microbes, which then thrive and create channels for nutrients that would not make it up the roots otherwise. Molasses, specifically black strap, is a great potassium and magnesium source for plant as well. I would first poor 2 gallons of distilled through her for a rinse. Would let that drain off well, then water her with the Molasses / distilled mix. Until runoff. Before have doing any of this, I would do the most crucial thing that will answer your question quickly. I would take my Medina Hasta La Gro, 6-12-6, follow the instructions for foliar feeding. Make a solution 75% of what the instructions call for. I would isolate not the best Cola nor the worst. Carefully give this Cola and this Cola only a foliar feeding using misting bottle. Honestly, I'd do the whole plant, but if you're leery, do 1 cola. Put her near the lights but not direct. Temporarily turn off any fans and allow the meal to soak in. It is extremely non residual. Won't ruin your buds. You won't have to do it again, but you will, your next grow in vegetative state. Cause the stuff is awesome. It is nearly impossible to burn. Salt build up is minimal. Try this my friend. I bet you anything it will work.
I understand the pic examples I'm including are totally different stage. But the point is speed of recovery. The mutilated looking twigs were plants a buddy of mine was beating every way silly in a solo cup. He'd gone back and forth between deciding they needed nutrients, to flushing them. He had no idea where to go. He gave them to me. I did exactly what I just described to you except also repotted and in only 4 days, they were completely different plants. Bastards turned out males but were part of my journey of learning and success. I will only start and grow seeds from seed banks now, auto or fem. Good luck, but I don't think you'll need it. Try this and nothing luck related to it, just Botany and the way the grow will go
What a difference! So cool to see plants come alive like that. So the distilled 7.0 neutral should be ok?