gouramis have interesting personalities sometimes. i had a male blue gourami that terrorized all. i have a 3 pearls that were very outgoing...until i moved the 3 moonlights they lived with into another tank. they hid mercilessly. i put the moonlights back, and the pearls seem much more comfortable again.
maybe the kissers are intimidating them. i only have had a couple of them...and not successfully. but they didn't cause any problems with my other gouramis. i wouldn't think your 3spots would *hide* because "gouramis don't like gouramis." generally, such a statement is said against 3spots attacking other gouramis, and 9 times out of 10, i believe males are the culprits. so i would expect your 3spots to be "on the attack," as it were, if there were a problem with this grouping.
anyway, i'm not sure how to help. you could consider adding another and see if it makes them come out more? are yours male? female? unsure?