Ouch. Your params where they supposed to be? Prazi can crash bio filters I heard, that motoro seemed to have turned for the worse pretty quickly.
Unfortunately I think you are in crunch time right now. I feel like you immediately have to start mitigating, and your next moves will have to be very careful and planned out. No lights, no stressors, medicate when you are sure you need to with what you need to, I personally wouldn't shock with massive water changes but I would consider 10% twice a day if you can, and pray man. Did you by chance spray aerosol near the tank or have someone spill something in it or something? I find the quick decline to be uncharacteristic of a stray pathogen, I feel like there must be a catalyst. Maybe others can chime in but if it were fungal that is pretty damn aggressive for fungal isn't it?