I honestly think that is too many cichlids for a 55 gallon, but I'm sure some others will disagree. For a while, I kept 2 BPs, a severum, and a firemouth in a 55 and once they hit adult size they seemed crowded. I ended up moving them into a 75 gallon and they not only looked a lot more comfortable and relaxed, but aggression was next to nothing after the upgrade. I would suggest choosing 2 fish out of your list instead of all 3. Any of those fish should be compatible with each other, with one caveat: it's been my experience that parrot cichlids often don't take well to new parrot cichlids. I've always recommended adding them at the same time, but if you try it, look for a new addition that is the same size or larger than your current parrot. JMO.
