The chefs have few pressure outlets; they're allowed limited internet access in order to research food, but they aren't allowed to disappear for a long walk, or hole themselves away with headphones, etc. since the show depends upon their engaging with one another. They can't even listen to music, since this would interfere with recording dialogue! One of the only ways the chefs can blow off steam is by drinking -- which only contributes to the exhaustion. To top it all off, they have been, by necessity, divested of their money to discourage independent forays out into the world and are kept isolated from other people (except the judges, crew, and the people they feed) which gives their world a surreal, hermetic quality.
Is it any wonder that they flip out when someone touches their toothbrush? But the most obvious effect of all the stress and exhaustion is that it seems to compromise the chefs' chief asset -- their imagination. That amorphous place from whence springs ideas, inspiration, solutions, sense memory, and innovation. True imagination can be nurtured, but not taught. It can manifest through an intuitive understanding of how to juxtapose taste and texture, or through wild flights of fancy. Some chefs' imaginations give them a unique understanding of the emotional value of food -- the way in which it can provoke or comfort. For others, imagination leads them into arch, whimsical interpretations of culinary classics. Regardless, when people get stressed out and tired, imagination is often the first thing to go.