What type of gouramis are they? If they are one of the Trichogaster trichopterus color varietes then I'm not surprised. They are pretty aggressive and probably see the rams as invading their territory. Especially since you added the rams after the gouramis were already established. That probably wasn't the best idea. If I were you, I would try to rehome the offending gourami, or all of the gouramis, especially since the rams are a pair. Maybe they will breed for you if given a more peacefull environment. Or return the rams.