RE: Bad Fuel - how?
Squeeze all the air out of the bottle if you can. Put the stopper back in if you can, too. Some of the newer fuel bottle tops available seal the bottle so no air can get into the bottle. If your still using a can, like Power Master has, you may have a on going problem.
Get the air out and keep it out.
This also seems to get worse with the more nitro in the fuel. 10% fuel seems to last forever, 30% seems to last a week if not sealed properly.