The mother of the two red panda cubs that passed away last month has died, the Santa Barbara Zoo announced.

Ruby, a 2-year-old red panda, was admitted to the animal hospital over the weekend and passed away Wednesday morning.

A zoo spokesperson said on social media that it is believed that Ruby had Addison’s disease, which affects the body’s ability to produce cortisol and other essential hormones.

“Ruby was likely in the very early, undetectable stages of the disease, and the extreme physiological stress of pregnancy, birth, and lactation likely triggered an acute Addisonian crisis,” a zoo spokesperson said.

“Coming so soon after the loss of her newborn cubs, this is a devastating blow to our entire Zoo family. While pathology is underway to better understand her illness, veterinary teams do not believe her condition was connected to that earlier loss.”

Kristen Wieners, director of Animal Care, said on social media Ruby received the “best care possible” after the animal team noticed she needed “extra care.”

The zoo brought in outside specialists and ran tests, but “couldn’t pull her through that,” Wieners said.

“We really appreciate and thank you for all of your support during this difficult time,” she said.

Ruby welcomed twin red panda cubs with Raj, a 4-year-old red panda, in early July, much to the zoo staff and community’s excitement.

Red panda cubs are classified as endangered, with fewer than 10,000 mature red pandas believed to remain in the wild.

But one of the pair’s cubs died on July 21, and the second one died a week later. Red panda cubs have an infant mortality rate as high as 40% in their first year of life, according to zoo staff.