There isn't an H. severus in that tank. The big blue one does look like the potentially undescribed turquoise-colored species from Manaus: http://www.amazon-exotic-import.de/Gallerie/Cichliden/Seiten/Heros%20spec.%20Turqoise%20Manaus.htm
I'm sure you know more than me. My ignorance is evident by my post"s original question. But the exporter in brazil had these listed on his stocklist as heros serverus. That exporter has been in business for 3 generations exporting amazonia pesces. So I tend to believe they are heros severus. I hope others chime in on this.