A male designer was treated by a psychologist after he had a "bad episode" at New York's Parsons School of Design, reports the New York Post.
The designer "seemed too nervous" and decided he should exit the show.
Meanwhile, a female designer apparently "disappeared" from the set after she was placed at the bottom following a challenge, but it was discovered that she was staying in her apartment.
A source claimed: "She just ran off in the middle of the night. The next morning she wasn't in her bed, her suitcase was gone. Producers went to her home, and her doorman said she was upstairs but didn't want to see anyone.
"We lost two designers in one day," the source added. "This has never happened. They seem to be under a lot more pressure."
Project Runway's judge Michael Kors was said to have given the other contestants a pep talk last week after the incidents.
Project Runway will return for its tenth season on Lifetime.
Watch a video clip of Project Runway below: