Well bal it depends on how long you have had these fish. I mean you can't go out buy swordtails earlyer in the week and acspected the bigger fish is pregnate. One way you can tell if ther pregnate or already had fry just look in the tank or get a breeding tank and put the "pregnate" swordy in there. It may seem funny to move the fish to anouther tank just because its pregnate but it will keep most of your fry from dieing. Then when ther big enough put them back in to the main tank. Oh be sure the other fish you have in ther will not eat them or wait till they simpley not "bite size".
Sorry you lost a loved one at least its in a better place now.
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55 gallon tank
2 giant danioes
3 female swordtails
1 male swordtail
3 imature swordtails
1 rainbow shark
1 plecostomis
2 male guppies
10 gallon tank
2 pregnate female guppies