After Mary Cosby's son Robert Cosby Jr.'s sudden death this week, "The Real Housewives of Salt Lake City" cast has put old wounds on ice.

Sources familiar with the situation tell TMZ ... the SLC housewives have set aside past fractures and on-camera drama to rally around Mary during an absolutely devastating moment of her life. We're told any lingering tension from filming or prior seasons simply doesn’t matter right now.

Our sources say the outreach has been unanimous. Every cast member has contacted Mary in some way ... some stopping by in person, others checking in consistently by phone and text. We're told there's been no hesitation and no division when it comes to supporting her following Robert's death.

While the franchise is known for explosive confrontations and shifting alliances, our sources say this is a moment of total unity. As one source put it ... "This goes beyond the show."

We're told the women have made it clear they’re available for whatever Mary needs ... whether that’s emotional support, quiet company, or simply space ... with reassurance they're close by.

Mary, meanwhile, is leaning heavily on her faith. Our sources describe her spirituality as a guiding force right now ... helping her process the unimaginable loss day by day.

We broke the story ... police responded to a possible overdose in Salt Lake City on Monday and found Robert dead. Dispatch audio later revealed someone attempted to administer Narcan at the scene, but it was unsuccessful.

As we first reported ... 'RHOSLC' is in pre-preproduction and wasn't shooting at the time of Robert's death. Filming was expected to begin this week, but production has been postponed in light of the tragedy.