Definitely transplant into a bigger pot, preferably with some quality soil and perlite. I'm not that familiar with making mixes, so I can't really comment on where it went wrong. If it's been a while since your last transplant, could be that the buffers ran out.

You can try diluting some crushed dolomite lime and watering with that to try and bring the ph of the soil back up. But the transplant will also help a lot.

Why are those CFL's so far away? I'd say 4 in. max...