Answer:
As long as Mitch acted in good faith and tried to make the best possible decision regarding all available information, and his decision was something that any other person could have made, his mistake has to be considered a bad or negative business judgement (business judgement rule). He thought that his actions would benefit the corporation, but he was wrong and the corporation lost money. That types of mistakes are considered normal and just that, mistakes that anyone can make.
In regards with the second issue, that Mitch is a shareholder and a director of a firm that will directly compete with Numero Uno, he must inform the board about this and resign to either Numero Uno or One of a Kind.