Last week, during the Rakhi special episode, a major tiff happened between the mentors when it was time for elimination. All the four were divided on the elimination that week and things came to a standstill when they eventually decided to not speak with each other.
This led to an ugly spat between the four and as a foregone conclusion they just left the shoot. This might appear to be a publicity gimmick but the fact of the matter remains that they are just not in talking terms with each other. Although on screen "they are all cool and at peace with each other" but the insiders are just waiting for the volcano to erupt any moment now.