Dead Indian Gourami

What is the gender ratio of the 6, and was the one that died male or female?

I know that with some species of gouramis, males can be very territorial (ie bully weaker males to death) and very insistent about breeding (harass females to death if there aren't enough females to spread the males' attentions round). But I don't know enough about Indian gouramis to say if they are one of the more aggressive species.
Seriously Fish does comment that "This is not a very vigorous species" and that it should be kept with "inoffensive species". What is in the tank with them?

It does sound as though the weakest fish was bullied to death, I'm afraid.

The other fish shouldn't cause any problems, with the possible exception of the male swordtails, which can be aggressive, though that's mainly towards each other.

If things are peaceful at the moment, I would leave the gourami numbers as they are.