I am very sorry for your loss. It is hard to say if taking her in the night before would have helped. A slight discharge isn't a major sign of alarm. I am thinking he probably had something brewing for a while. Signs would have been weight loss...soft or hard stools...decrease in appetite. Without a necropsy (exam of her body by your vet), you may never know. You also have to take into consideration if you got her as an adult, her age...their lifespan is roughly 5-7 years on the average so she may have been geriatric if she was an adult. Again I am very sorry for your loss.
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Good Luck &
Best Fishes
