... other aquarium strain convicts. Geographical variants from various collection points, bred over many years back & forth & back again. Inbred to the 'enth degree. Some could even be crosses within the same genus, Amatitlania.
en.wikipedia.org
No different than what took places several decades ago between "red devils" and "midas" cichlids. At the time those collecting and exporting/importing (back in the 1960's) believed that they were the same species of cichlid, only to find out much later that they are not. This is why aquarium strains can now vary so much.
A buddy of mine in town used to comment about how my white "convict" didn't look like a wild type convict, and he was right, it looked very similar to yours. What it's actual genetics were is anyones guess, but my guess is that he was simply a cross between different aquarium strains.