The death of an 18-year-old orca at SeaWorld San Antonio is bringing negative attention back to the theme park. Unna died on Monday, SeaWorld announced , after being under constant care for months for a resistant strain of fungus called Candida. The exact cause of her death is still unknown, but because she's the third whale to die at the San Antonio park in the past six months, scrutiny from animal activists is intense.In November, a beluga whale died of gastrointestinal problems. In July, another beluga died after being born prematurely, the Washington Post reports."We were all saddened by these deaths, especially the animal care team that spent countless hours caring for these animals," SeaWorld states in a post answering questions about Unna's death. "After a review of each of these cases, none of the issues were related to each other, or to the care that the animals received, which is the care that SeaWorld is world-renowned for."These answers aren't enough for opponents of the park's practice of keeping orcas captive. Unna was the daughter of Tilikum, the whale featured in the 2013 documentary Blackfish, which showed the lives of killer whales in a particularly bleak light and blamed SeaWorld for causing Tilikum to become violent and kill three people.John Hargrove, a former SeaWorld trainer who appeared in Blackfish and has written a book speaking out against the park, told TakePart.com that SeaWorld's account of Unna's illness is false. "When I came back to the San Antonio park in March of 2008, she had already been sick for some time," he said. "She was already on high doses of multiple medications, including an antifungal and antibiotics, every single day."According to SeaWorld, Candida is an organism commonly found on whales and has been found to cause their death in the wild and in captivity. When conventional treatments failed, several experts in veterinary medicine, fungi, and nephrology came together to adapt a treatment normally given to humans into something for Unna.Naomi Rose, an orca researcher at the Animal Welfare Institute, told TakePart that Candida is not common in the species and blames Unna's illness on stress and a compromised immune system.Regardless of what is determined to have caused Unna's death, activists in California, are making headway in the effort to end the park's orca program. Earlier this year, the California Coastal Commission banned the breeding of orcas in captivity, as well as their sale, trade, or transfer. A month later, SeaWorld San Diego announced it will no longer feature its "Shamu" performances. Meanwhile, the park is adamant about its work in conservation, care, and rescue of marine animals. According to its site , SeaWorld has rescued 26,000 animals in over 50 years.