Not always hybrids but many times they are not great quality. It kind of depends.
Ok for a 55 gallon the best way to go is to pick 3 species of similar aggression. This helps you set up for a more successful tank. Yellow labs are a great choice, as are rusties and Ps. Acei. The ones you should really stay away from are auratus, chipoke, kenyi, and bumblebees. These guys get super aggressive as they get older and can wipe out a whole tank if they feel like it. Unfortunately these super aggressive fish are commonly sold to newbies. I see you already have a kenyi and auratus, it's up to you what you want to do with them.
Anyway for a 55 gallon you aim for about 3 species with 4-5 per species. It's best to keep 1 male to 3-4 females. These "rules" vary depending on the size and temperament of the species.
Also I saw your pictures of your tank in another thread. These guys will need a lot of hiding places to be able to get away from each other. Fake plants, flower pots and rocks make great decorations and help break up the line of sight.