When you cross species, color or humps are not the only things you are effecting.
You are also crossing immunity (or lack thereof) and other certain health traits, because the inner flora and fauna of those species.
I had been keeping cichlids for over 50 years, and never had a case of ducklips in any of my cichlids during that time.
Not until the "invention" of the flowerhorn, and now, with that invention, ducklips is almost as common as ich in cichlids. I believe crossing species has other consequences than simply appearance. The growing virulence of certain pathogenic bacteria may be one of those consequences, and I find this, more than just annoying.
Species from one area, may have evolved immunity because of temp, or water conditions, to certain bacteria, so randomly crossing with a species from another area in a situation where "survival of the fittest" doesn't come into play (like an aquarium), can do much to weaken the species, but also to make that pathogen stronger, and more resistant to environmental factors.