Red Wag Swordtail

I got a red wag swordtail. i thought it was a female at first but it has a black line on the bottom of its tail that looks like it might have been eaten off at the store. So question one… Could it be a male and if so will the tail grow back? Secondly. I’ve had this fish for about a month now with no problem. I have danios in the tank and I had a a couple of phantom catfish, a bumblebee catfish and an albino catfish. Oh and one male beta (who causes zero problems in the tank and I’ve only ever seen him frill his gills up for the first couple days when a new fish is introduced, but never attacking. I’ve had him for 3 months) Now i know my danios have breed a bit. I’ve seen them get pregnant and go down to the rocks to what I assume is laying their eggs. But I have 3 ghost shrimp in the tank so again I assume they get to the eggs before anything happens. I’m not really trying to breed them. Now one of them was just recently pregnent within te last few days and now the little belly is gone, and at the same time I think the male red wag swordtail platy starting attacking the catfish(except the bumblee. he hides) and eventually my flouresent red danio killing them all. after the initial attack the other danios joined in on the catfish but not the other danio. There’s only one red wag swordtail in the tank. Could it have been the danio laying eggs that set him off or something else? I know this is a lot of info but I want to know exactly what happened. I don’t want to get rid of the red wag swordtail. He’s been pretty cool until that happened and now he’s back to his old self. A lot of the fish stores are quick to blame the beta but he doesn’t attack anything. I know my little buddy. If anyone can help me I’d appreciate it.