Yes, your tank has too many gouramis for it not to be aggression really...I recently restocked my 55 gallon tank, and am noticing some aggressive tactics from one of my kissing gourami as well. Right now I have 12 zebra danios, 2 kissing gourami, 2 dwarf gourami, 2 gold gorami, 2 lavendar gourami, 3 dwarf rainbow fish, 1 rainbow shark and 3 plecostomas. So far they seem to be doing pretty well together, but there is 1 kissing gourami who likes to chase the other fish. I can't tell if he's just playing or being a bit aggressive.