Ph skyrocketed... 8.7 help...

So, I got some activated charcoal to add just temporarily to my filter, I think the stones I used released some heavy metals and that was causing my axolotl to be sick.

I removed the rocks and added the pre rinsed charcoal and voilà, from 7.6 to 8.7, the charcoal probably had residues from something.

What do I do now? I already tubbed the axolotl and did a, I dunno, 90% water change.

Should I throw all the filter media and start again? Or can I use almond leaves and driftwood and just let the bacteria feed again?