Kissing gouramies are diffecult to feed. They probably won't take live food and there eating habbits are a little different from other fish. They tend to suck (almost filter feed style) on floating flakes. They litterally swallow a lot of water at the surface and hope that some food will fall in their mouth.... It could take them several weeks to get used to eating in a community tank as usually the other fish will finish the food before they get to it... If the gourami is still young, they may not survive this experience.
couple of methods I have had a lot of success with:
1- Tubfix freeze dried cubes.. They tend to be a little harder for fish to eat so they float for a long time giving the kissing gouramies a chance to munch on them...
2- Use fresh vegetables, carrots, cucumber, lettuce, zuccinie etc... blanch the vegetables lightly by putting a couple of slices in a strainer and pour boiling water on it then dump it in the aquarium.... It might take them 24 hours to start eating it but they eventually do.... Don't boil the vegetables otherwise you will make them too soft and other fish will eat them first. you want them relatively hard so they don't get eaten quickly...