In Dwc for seedlings start them on about 5ml each part ,if you use a 2part nutrient that is. It shouldn't be strong for the first few days after it sprouts.
What nutes do u use?
After a few days to a week add a little bit more, not 5ml each part this time tho ,maybe 2-3ml.
Once it gets bigger youl see it feeding (ppm's will drop slightly)
Once you see it drop slightly every day you know you're on the right track.
If ppm's rise every day or anytime you check then the mix is too hot and u should dilute the solution.
For roots and to prevent rot I'd suggest keeping Res temps below 24c and getting some Rhino Skin from advanced nutrients and something like great white powder. Great white is mychorziae which help protect roots. I only add 5ml Rhino skin to 15litres of water and if I was using great white powder I'd only add the tip of a sugar spoons worth each time I changed the Res.
Rhino skin is a silica which plants need to grow big and strong and it also protects the plant from pests and bacteria.
I use advanced Nutrients tarantula liquid which is expensive , it's nearly 25 pounds for 250ml but it works well.
If the plant roots youl be ok just keep her on a light feed until it does tho , 200ppms will be ok until she roots. Snip the tips of all the leaves about a quarter of leaf. It stops the plant putting effort into fattening out it's leaves so it will then concentrate on rooting. Keep it humid or spray water on it now n then and you should be fine. Hopefully in about 7to14days youl have roots again.
If you want , and if you can't get hold of mychorziae powder/liquid then try and get 3% hydrogen peroxide from a chemist.
Sometimes it's needed but you don't add alot. It's better to read up on h2o2 (peroxide) and find out about the application and how much to add. It's been a while since I had to use it so I'm not the best to ask really.
only use peroxide for root rot if you can't get hold of the other stuff , you can also use it to clean your equipment like airstones n airlines n that way you won't be adding the bad bacteria back into the Res.
For cleaning all that stuff 1 capful of bleach in hot/warm water will also kill bad bacteria so soak your equipment before setting things back up just incase.
Your leaves won't repair themselves if there burnt but the new growth will be fine so I wouldn't worry too much just now about the condition of the now clone. She will sort herself out once she gets some roots again.
Hope this helps.
If not let me know.
If there's anything else you need to know just ask bro and if I can help I will.