Help please!

I own two female Dogo Argentinos from the same litter, both approximately two years old, who have always had a good relationship. However, they recently had a intense fight. It has been close to 19 days since we started keeping them apart. Despite our efforts to reunite them, they continue to show aggression by growling and displaying a desire to fight. Additionally, both animals have not been spayed. Is this a common issue, and what can I do to foster harmony between them once again?