add up 20 litres of hi-octane and remaining 25 litres of supreme from PSO or SHELL, it was just bad fuel not the plugs or the ignition or injection system. top up again at half tank and you will be back to normal.
since you have not mentioned your location please see if Caltex fuel additive is available in your town. There are some good quality fuel additives available in KHI LHR RWP & PSHWR