Widow fish die quickly in fish bowl

Though some aquarium shops are stocking a large number of widow fish , these fish have a limited lifespan.
A local aquarium had sold the black and white widow fish for Rs 50 a pair.
Initially the fish were flourishing well, however the fish owner was not in goa for 4 days.
Though she had put some holiday food in the fish bowl, when she came back from the holiday, both the widow fish had died.
In comparison betta, fighter fish are far more hardy, surviving for more than 1 year in far worse conditions.

Swordtail fish may not survive air transport

A hobbyist was doing research on keeping various live bearer fish, found that the sword tail fish died rather quickly due to unidentified reasons. Most of the local stores are not stocking any swordtail fish, so the fish was purchased in Mumbai and bought to goa by air, A pair of swordtail fish were costing rs 50, however the fish with the swordtail , died within 48 hours of reaching goa. The fish was transported by air.
The other fish appears to be in good health .
Now the hobbyist is left with one swordtail and one sunset platy as one fish in each pair has died due to unknown reasons.
Any tips for keeping swordtail fish in a fish bowl will be appreciated.Local suppliers in panaji, goa can also contact.