Plants went into shock/underwatered? They are dying need advice

So for the past 3 months, I've been doing my very first grow. It has been so much fun, I have learned a whole lot. But right now these guys are in deep trouble due to my novice mistakes. I'll explain what happened but there's no point beating myself up about how I could have avoided this, I'm actually excited about my next grow and doing every step right by the books. But anyway here is the situation:

My plants had been vegging out for a good 2 and a half months. They were healthy, the only real health problems coming from some nutrient burn and overwatering, slightly under-watering at times. I put the plants in hot miracle grow soil to begin with, only because I didn't know any better. They were still doing great but the plants had run out of room to grow. Also around this time I decided to change their light cycle to try to induce flowering. They were about 2 weeks into their new light cycle when this happened. I had an impulse to transplant them so that they had more soil to grow down, I bought more hot soil, this time I bought moisture control miracle grow soil. Well shortly after their transplants they looked extremely droopy and wilted. Another important thing to note is that I live in New England and this is an indoor grow, so its very possible that they go through some radical temperature changes every night despite the fact that I keep my thermostat around 70 nonstop. Since then they have only gotten worse. I gave them a bunch of water, they are getting permanent light at the moment. I want to know what I can do from here as far as damage control. I would like to keep them, at least part of them so I don't have to completely start all over again.

You watered, wait a bit, might have to do some pruning.

This morning they looked a little...I dunno...more dying. Little bit drier in many leaves, soil still damp, still completely wilted. I gave them more water and I'm waiting more. But a little bit of hope left me after checking them.

this time I bought moisture control miracle grow soil.

Little bit drier in many leaves, soil still damp, still completely wilted. I gave them more water and I'm waiting more. But a little bit of hope left me after checking them.

Huh, that's a bitch. Bought moisture control soil and then drown the plants.

That soil was a bad idea, ironic too. Well I think they are losing even more life, the stems are turning white. Whats the best option now? How about clipping the leaves, repotting them in good soil and trying to start them as veggies again?
?

Starting to think they got a disease like fusarium wilt and then it kept sucking the life out of them.

I took some more pics. What scares me is this growth of white that is not powdery at all, but very superficial. And it grew, a white curse spread to all the greenness... sigh...I had another photoshoot, let me know what you guys think. Please and thankyou fellow growers for any responses and help.

Clean up start, over.

Ohh attachment, the source of suffering. :(