Does Rapps (your source) know how old they are? That's pretty small for a Synspila; they get big. The female in particular seem to go through "Kodak" moments where they kill anything and everything in the tank, including their mate.
Though a lot of literature sets them up as being reasonable, I don't. They're probably one of the Flowerhorn base fish and act accordingly. I'd separate them.
Are they colouring up nicely? Take a look at my femael Syn. at over 10 inches in the body. She killed two of her own young that were over four inches easilly, and almost killed her mate, who she had spawned twice with in a tank over 200 gallons.
Yes, there are personality differences and even mellow Jaguars, for instance. She has no issue with my male Oscar but killed a female Oscar her own size by pummelling it with her head.
"Conspecific" they are in a big way!