Unna, an 18-year old Orca whale, died earlier this week at SeaWorld's park in San Antonio, Texas.

According to a statement from SeaWorld, "Unna had been under the constant care of the SeaWorld veterinary team and outside experts for the past several months," and "suffered from a resistant strain of a fungus called Candida."

"Candida, and fungal infections in general, are found in wild cetaceans," the statement said. "A necropsy will be performed to determine the ultimate cause of her death."

Unna is the third whale in six months to die in this particular park. "November saw the death of Stella, a beluga whale that was being treated for gastrointestinal problems," The Washington Post reports. "And in July, SeaWorld-goers mourned a newborn beluga who died after being born premature."

Since 1991, 14 whales have died at the San Antonio SeaWorld.

A female orca whale such as Unna is expected to live roughly 30 to 50 years in the wild -- so what could cause her life to be cut so short? What about the other whales who've recently passed at the San Antonio SeaWorld?

While SeaWorld claims Unna was sick for a few months, John Hargrove, a former SeaWorld trainer-turned-activist, thinks there's more to the story.

"She's been very sick for at least eight years," Hargrove told the Times of San Diego. "This isn’t something that’s new, that they say came up in just the last couple months. That's total BS."

While SeaWorld said Unna's definitive cause of death is yet to be determined, some marine biologists and activists have suggested the stress of being in captivity can cause a whale's immune system to weaken, therefore making it difficult for the animal to fight off infections such as candida.

"What bothers me about SeaWorld's PR rhetoric surrounding Unna's death is the implication that she died of something 'natural/normal,' which was in no way related to her being in captivity," Naomi Rose, a marine mammal scientist, wrote in a post. "The PR message went RIGHT for the statement that 'this condition is found in wild cetaceans.' However, Candida does not cause serious illness - pretty much in any taxon it affects - unless the immune response is compromised, as with stress.

"SeaWorld is spinning this situation, rather than telling the truth, and it does no one -- not the public, not science, not captive orcas, not SeaWorld -- any good," Rose added.

Since the release of the documentary "Blackfish" in 2013, SeaWorld has been under a heightened level of scrutiny, which is likely responsible for its park attendance to plummet by 84 percent. As MTV reported in November, SeaWorld has faced widespread criticism for drugging and interbreeding its killer whales.