There is trouble brewing between Glee stars Naya Rivera and Lea Michele, sources reveal in the new issue of Us Weekly. The tension heated up when the two actresses got in a major altercation on set on April 15.

"They're always icy to each other, a show source tells Us. "Naya is jealous that Lea is the show's main star… There is a lot of sighing and eye-rolling between them." 

Adds another insider: "They talk behind each other's backs -- a lot." 

It's been a tough time for both women as Rivera, 27, recently ended her engagement to rapper Big Sean, and Michele, 27, is still recovering from the July 2013 overdose death of her late boyfriend, Cory Monteith

For more on the songstress' spat, watch this week's Hot Stuff video, as explained by Us Weekly entertainment director Ian Drew and Rocky on Broadway stars Andy Karl and Margo Seibert

Other stories in the roundup: Katy Perry's hot fling, the latest on Juan Pablo and Nikki, Padma Lakshmi's new man, and more!