JI No 3 is for more mature plants. It's too nutrient rich for your plant so is burning it. Give it just water until it looks healthy then start with the nutes at a low dose. If it wasn't an autoflower you could grow it out and let it get big enough to flower.
Normally you'd start on JI No 1 for seedlings, No 2 for cuttings, and No 3 for mature plants that can take that much nutrient.
And you should really add some perlite to the mix to make it dry out quicker reducing the risk of roots rotting.
Don't worry - all part of the learning process.
The one thing they need is time to recover - which is the one thing autos don't really give you. They should finish, but the whole time they're stressed they won't really grow, so the yield might be small.
A lot of this game is one step forward, two steps back. Don't lose heart - just keep at it and keep a notebook of all the things you've done which work.