Having just seen Izlet's thread about her cats' relationship I thought I'd ask for suggestions about mine.
Two of mine are sisters, 3 years old, not pally any more but generally amicable. One is a bit dozy, very lovable & affectionate; the other, who was always Top Cat, is very smart, ignores catnip, plays fetch & calls for attention when she wakes up in an empty room. Third cat, coming up for 2, is a bit mad, very lively (looks to have some Bengal blood) & loves playing chase but nobody else does.
Top Cat recently started growling & swiping at mad cat. I don't know why it started but now mad cat seems to be going out of her way to annoy Top Cat, mainly by lurking under bits of furniture & pouncing as TC walks by. TC is not amused but instead of standing her ground she runs, so mad cat gets her chasing 'game'; but TC is becoming increasingly upset about it, behaves a bit anxiously sometimes, & has stayed away from the house overnight twice recently (once for 24 hours & once for 36 hours, though both times she was starving when she came back so maybe was shut in somewhere)
TC also spits at her dozy sister now when dozy one is just coming to touch noses 
So, like Izlet, I'm wondering if getting another cat might help settle things down - I'm thinking another very lively one for mad cat to play chase with might get her off TC's back?