The pair and juveniles certainly look to me like a real pair of Heckels and the fry look like they could only be those of two real S. discus.
I think so few who have tried or hoped for their Heckels to spawn, myself included, never provided them a pH of about 3.5 and no measurable hardness. If Heckels are not kept in that type of water then breeding them stand virtually no chance. I believe the same applies to Pterophyllum altum. These fish have evolved to thrive in water conditions which scare the hell out of most Discus keepers and that almost automatically precludes successful breeding.
I have only kept some small species in water that extreme with Cattapa leaf litter.
My 20 long has about 20 Poeciliocharax weitzmani in RO water not passed through a mixed bed deionization filter so the TDS is >15 ppm from water taken from their tank and the pH is always between 3.5 and 4.0. These little ambush hunting, oddball Tetras eat only living food for me. Keeping Discus sized aquarium water with these chemical attributes is difficult and demanding work few dare to try. The fellow who bought my 10 Heckels is providing them these water conditions and although he has not gotten any further with breeding the pairs he kept they sure are a lot prettier than when I was keeping them in tap water. It helps when you have a 300 gpd RO unit because water changes are more important than ever when working with such extremely soft acid water.
he uses Muriactic acid to lower the ph and some Cattapa leaf litter. These leaves are good for contributing the weak organic acids and tannins which give black water it's name.
I have no way of proving this but I suspect Heckels begin breeding later in life than either S. aequifasciata and S. haraldi.