This seedling would fail my "quality control" and would be culled immediately and without hesitation, whatever the reason for its appearance.
Some seeds just aren't meant to be.
You could try and nurse back to normality, but in my experience, 35+ years, seedlings like this do not ever recover.
Age is not a factor, just bad genetics.
If it were the last seed of a very special strain of cannabis, I would do everything in my power to get it growing, but if I had more seeds of this particular strain, chop, chop is the only practical course of action. You could spend a lot of effort trying to get this seedling to perform and end up with a lot of time and money spent on something that never grows or flowers properly.
In nature it is "survival of the fittest". This seedling is not very fit at all. Harsh maybe, but bluntly true. Sorry.
pH and germination did not cause this. It is plainly and simply, "a bad seed".
Hope this helps,........
Organoman.