Eyewitnesses reportedly spotted Lowe and Giudici getting into it at The Sayers Club in Los Angeles on March 18 while celebrating Lowe's first Dancing with the Starsperformance and arguing again only two nights later when walking back to the apartment complex where they have separate apartments.
"About an hour after they arrived, Sean and Catherine were in a corner, and she was clearly mad at him, yelling at him," a source told Life & Style.
"Sean was trying to talk to her, but she didn't want to hear it. She was fed up with him and rolled her eyes. Then she started crying, wiping her eyes and looking away from him. She was shaking her head and hands at him."
The pair's argument at the club reportedly lasted for about a half-hour.
But another source apparently saw the blowout fight coming, as there was a "chill" in the air earlier that evening between Lowe and Giudici at the Planet Dailies restaurant -- where the couple was attending a Dancing with the Stars after party.
"They sat side by side at a table at the back of the restaurant with some friends, but they hardly talked," the second source told the magazine.
"Catherine was texting on her iPhone while Sean was drinking beer and toasting with his buddies that he had flown in from Dallas. He was being very goofy, very frat boyish, and Catherine looked like she didn't want to be there."
Lowe and Giudici's second argument reportedly took place a couple of days later when they were walking home one night to their separate apartment units.
"I could hear Catherine talking to Sean, and she sounded annoyed," claimed an insider, Life & Style reported. "They were having a disagreement about something. I heard Catherine say, 'That is annoying, Sean. Why do you say that?' Sean was trying to calm her down."