2003 Toyota Tercel timing belt replacemente

Hello, I have just change the timing kit to my car but two or three days after sudenly the power of the engine fall dawn. Checking it, we found that the spark plugs were wet and corbonized. I replaced them but four day after ther were damaged again. It is possible that the changes and setting of the time belt could cause the problem with the spark plugs or it was just bad luck.
Cheers