Sometimes when a female is near delivering her load of babies the other fish in the tank will harass her while trying to eat the fry, that could have lead to deadly aggression and account for low number of fry. She could've had complications during birthing the fry and died, hence the low number of fry. She could've died of natural causes and the other female be the mother of the fry and she may just be hungry... I doubt if it was tuberculosis, that is actually not as common of a fish disease as people let on, and fin rot, even severe would take more than a day, I'm almost positive.
Maybe the others will settle in and relax.
