My gouramis are dying

Question
Hello there,
I am in desperate need to find help for my gourami's. I started my 50 gall. tank in June 2012. In July, I bought some gourami's and they have been doing really well until now. This month I have lost 3 and it looks like I will be losing a couple more. Near the end of their life, the have extremely swollen bellies, their fins look frayed. They are also extremely lathargic and hardly have an appetite.
When the first one died, I did a disease treatment on the tank for a week and then did a 25% water change. However, that really did not seem to work.
I need help!

Answer
What species of Gourami fish do you keep? What are your water parameters?

Gourami fish are basically cousin's to the Betta Splenden and males do not get along with each other without a lot of females and territories. For one male there should be at least four to five females to prevent the male from harassing them.

Males - Brighter distinct color, bottom fins are pointed.
Females - Silvery with not as distinct colors as male gourami. Bottom fins are rounded.

I would check to make sure the ratio is correct. If you have too many males they probably are fighting even if you do not see quarraling.

Frayed fins suggest fin-rot or fin nipping. Fin-rot means poor water quality. Which leads back to the water parameters and male to female ratio.

Swollen bellies suggests bloat or dropsy. How much are feeding them? Overfeeding is a big factor in fish death. Adult fish should be fed 4 days out of a week, 2x a day (morning and night).