If it recovers it will take an extra few weeks to mature.

That looks like rockwool jammed into a black pot with some sort of ebb and flow system. Maybe just a huge drainage bucket?

If the first is true then the root bound thing may be worth looking into, but if the roots are too damaged you could be screwed. I used to use rookwool and had similar ph/root problems. Just flush with tested water and a light (seedling strength) fert.