You're thinking of hypergolic propellants like hydrazine and nitric acid. This is kerosene (RP-1) and liquid oxygen. Not particularly toxic, just hot as hell.
The deluge system in shuttle launches was for the flame trench and sound dampening to avoid the air pressure from the noise damaging the vehicle, not fire extinguishing.
You can see the launch tower get charred black, that's the fire protective paint.
It's not really possible to fight rocket fuel fires, just mitigate the damage.
