Feliway is one of those things that works for some cats but not for others - but when it does work, it's like night and day. It can be horribly frustrating to have cat fights breaking out on a regular basis. Have you ruled out any additional health problems (such as urinary tract infections)? Sometimes adding an extra litter box somewhere else in the house can help curb the behaviors (especially with three cats in the house - the little hooligans in my house make a show of ambushing one another while on the toilet!). Also, make sure each cat has a separate safe space designated as "theirs" that they can retreat to when they feel bullied or put out by another cat - it can be as tiny as a box or as large as a room to themselves. Try to figure out where the behavior is stemming from - if it's a litter box ambush issue, for example, place the diffuser near the box. If it occurs most often in the living room while the kitties are vying for prime nap time spots, place it in there, and so on. It should help throughout the house, but it really adds that extra, concentrated punch when it's located near where the bulk of the worst behaviors are occurring.