Post a picture and or short 20 second video of the sick fish.
Have you checked the water quality for ammonia, nitrite, nitrate & pH?
If yes, what were the results?
Have you added any new fish to the tank in the last 2 weeks?
Have you done a water change and gravel cleaned the substrate in the last 2 weeks?
If yes, how big was the water change?
Dropsey is an internal infection that causes the fish to bloat up rapidly (usually overnight) and is normally caused by bacteria or sometimes by protozoa. The scales might stick out from the body, the fish will stop feeding and either sit on the bottom of the tank or hang out by the surface near a filter outlet, and they usually do a stringy white poop. They normally die within 24-48 hours of these symptoms appearing.
Depending on what caused the problem will determine the course of treatment. In Dwarf Gouramis (Trichogaster lalius) it is commonly cause by tuberculosis (TB), and there is no cure for this.
Don't bother treating the tank until we have a picture of the sick fish and can confirm dropsy or something else.
The fish might be getting bullied by the other one.
If you have a camera or a mobile phone, have the flash on, have the tank and room lights on, and open the curtains so more light comes into the room. Have the camera resolution at 2MB and then click away.
Take a number of pictures and put them on your computer, then go through them and put one that clearly shows the issue on here.