A bad tank doesn't cause low pressure. It only causes the pump to cycle on and off rapidly. You have to check the air in the tank when the pump is off and all water is drained out of the tank. The pressure gauge on the water line must read 0 when you check air in the tank with a car tire gauge. Then 50 PSI is too much air for a 40/60 pressure switch. You only need 35 to 38 PSI air with a 40/60 switch.
An increase in electric use means your pump is running more than it should. The tube to the pressure switch can be clogged and the pump won't come on or off at the pressure needed. Dirty water and high electric can also be from a hole in the drop pipe in the well. Rapid cycling will also cause high electric use but that should be obvious to see.
I would put on a new pressure gauge, get the correct air pressure in the tank, and clean out the tube to the pressure switch. Water surrounds the bag in some pressure tanks and the air can't get out because the water is higher pressure and trying to get in the bag. So you lose the air when the power goes off after the tank is empty of water. This is the only way a power outage could affect the air in the tank.
You could still be having power problems as well. If your pump is only getting 115 volts instead of 230, it will give low pressure, run alot and use more electricity. So also check the voltage.