Can I replace 3 switches with one 3 toggle switch
Don't do it! If the devices are on separate circuits, you cannot "tie" them together.

If you're in the USA and use single phase service,  you've likely turned a 120 Volt circuit into a 240 Volt short-circuit. You've directly connected the two legs of the service, causing a short-circuit. 

The switch is intended to control three branches of a single circuit.